Research Publications
Publications are listed in reverse chronological order.
2023
- \mnrasRotational and radio emission properties of PSR J0738-4042 over half a centuryLower, M. E., Johnston, S., Karastergiou, A., Brook, P. R., Bailes, M., Buchner, S., Deller, A. T., Dunn, L., Flynn, C., Kerr, M., Manchester, R. N., Mandlik, A., Oswald, L. S., Parthasarathy, A., Shannon, R. M., Sobey, C., and Weltevrede, P.Oct 2023
- arXiv e-printsThe second data release from the European Pulsar Timing Array: VI. Challenging the ultralight dark matter paradigmSmarra, Clemente, Goncharov, Boris, Barausse, Enrico, Antoniadis, J., Babak, S., Bak Nielsen, A. -S., Bassa, C. G., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Desvignes, G., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Graikou, E., Grie, J. -M., Guillemot, L., Guo, Y. J., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Karuppusamy, R., Keane, E. F., Keith, M. J., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Main, R. A., Mickaliger, M. B., Niţu, I. C., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Quelquejay Leclere, H., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Speri, L., Spiewak, R., Stappers, B. W., Susarla, S. C., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Venkatraman Krishnan, V., Wang, J., Wang, L., and Wu, Z.Jun 2023
- arXiv e-printsThe second data release from the European Pulsar Timing Array: V. Implications for massive black holes, dark matter and the early UniverseAntoniadis, J., Arumugam, P., Arumugam, S., Auclair, P., Babak, S., Bagchi, M., Bak Nielsen, A. -S., Barausse, E., Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Caprini, C., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Crisostomi, M., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Fastidio, F., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Gualandris, A., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Khizriev, T., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Middleton, H., Neronov, A., Nitu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Postnov, K., Quelquejay Leclere, H., Rana, P., Roper Pol, A., Samajdar, A., Sanidas, S. A., Semikoz, D., Sesana, A., Shaifullah, G., Singha, J., Smarra, C., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Steer, D. A., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., Truant, R. J., van der Wateren, E., Valtolina, S., Vecchio, A., Venkatraman Krishnan, V., Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.Jun 2023
- arXiv e-printsThe second data release from the European Pulsar Timing Array IV. Search for continuous gravitational wave signalsAntoniadis, J., Arumugam, P., Arumugam, S., Babak, S., Bagchi, M., Bak Nielsen, A. S., Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Ferranti, I., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. M., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Manzini, S., Mickaliger, M. B., Nitu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Quelquejay Leclere, H., Rana, P., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Singha, J., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Venkatraman Krishnan, V., Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.Jun 2023
- arXiv e-printsThe second data release from the European Pulsar Timing Array II. Customised pulsar noise models for spatially correlated gravitational wavesAntoniadis, J., Arumugam, P., Arumugam, S., Babak, S., Bagchi, M., Bak Nielsen, A. S., Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Niţu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Quelquejay Leclere, H., Rana, P., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Singha, J., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Venkatraman Krishnan, V., Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.Jun 2023
- arXiv e-printsThe second data release from the European Pulsar Timing Array I. The dataset and timing analysisAntoniadis, J., Babak, S., Bak Nielsen, A. -S., Bassa, C. G., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Desvignes, G., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Karuppusamy, R., Keane, E. F., Keith, M. J., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Main, R. A., Mickaliger, M. B., Nitu, I. C., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Samajdar, H. Quelquejay Leclere A., Sanidas, S. A., Sesana, A., Shaifullah, G., Speri, L., Spiewak, R., Stappers, B. W., Susarla, S. C., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Venkatraman Krishnan, V., Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.Jun 2023
- arXiv e-printsThe second data release from the European Pulsar Timing Array III. Search for gravitational wave signalsAntoniadis, J., Arumugam, P., Arumugam, S., Babak, S., Bagchi, M., Bak Nielsen, A. -S., Bassa, C. G., Bathula, A., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Chalumeau, A., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Dandapat, S., Deb, D., Desai, S., Desvignes, G., Dhanda-Batra, N., Dwivedi, C., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Gopakumar, A., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Gupta, Y., Hisano, S., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Joshi, B. C., Kareem, F., Karuppusamy, R., Keane, E. F., Keith, M. J., Kharbanda, D., Kikunaga, T., Kolhe, N., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Maan, Y., Main, R. A., Mickaliger, M. B., Nitu, I. C., Nobleson, K., Paladi, A. K., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Prabu, T., Quelquejay Leclere, H., Rana, P., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Singha, J., Speri, L., Spiewak, R., Srivastava, A., Stappers, B. W., Surnis, M., Susarla, S. C., Susobhanan, A., Takahashi, K., Tarafdar, P., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Venkatraman Krishnan, V., Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.Jun 2023
- arXiv e-printsPractical approaches to analyzing PTA data: Cosmic strings with six pulsarsQuelquejay Leclere, Hippolyte, Auclair, Pierre, Babak, Stanislav, Chalumeau, Aurélien, Steer, Danièle A., Antoniadis, J., Bak Nielsen, A. -S., Bassa, C. G., Berthereau, A., Bonetti, M., Bortolas, E., Brook, P. R., Burgay, M., Caballero, R. N., Champion, D. J., Chanlaridis, S., Chen, S., Cognard, I., Desvignes, G., Falxa, M., Ferdman, R. D., Franchini, A., Gair, J. R., Goncharov, B., Graikou, E., Grießmeier, J. -M., Guillemot, L., Guo, Y. J., Hu, H., Iraci, F., Izquierdo-Villalba, D., Jang, J., Jawor, J., Janssen, G. H., Jessner, A., Karuppusamy, R., Keane, E. F., Keith, M. J., Kramer, M., Krishnakumar, M. A., Lackeos, K., Lee, K. J., Liu, K., Liu, Y., Lyne, A. G., McKee, J. W., Main, R. A., Mickaliger, M. B., Niţu, I. C., Parthasarathy, A., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Samajdar, A., Sanidas, S. A., Sesana, A., Shaifullah, G., Speri, L., Spiewak, R., Stappers, B. W., Susarla, S. C., Theureau, G., Tiburzi, C., van der Wateren, E., Vecchio, A., Venkatraman Krishnan, V., Verbiest, J. P. W., Wang, J., Wang, L., and Wu, Z.Jun 2023
- \mnrasSearching for continuous Gravitational Waves in the second data release of the International Pulsar Timing ArrayFalxa, M., Babak, S., Baker, P. T., Bécsy, B., Chalumeau, A., Chen, S., Chen, Z., Cornish, N. J., Guillemot, L., Hazboun, J. S., Mingarelli, C. M. F., Parthasarathy, A., Petiteau, A., Pol, N. S., Sesana, A., Spolaor, S. B., Taylor, S. R., Theureau, G., Vallisneri, M., Vigeland, S. J., Witt, C. A., Zhu, X., Antoniadis, J., Arzoumanian, Z., Bailes, M., Bhat, N. D. R., Blecha, L., Brazier, A., Brook, P. R., Caballero, N., Cameron, A. D., Casey-Clyde, J. A., Champion, D., Charisi, M., Chatterjee, S., Cognard, I., Cordes, J. M., Crawford, F., Cromartie, H. T., Crowter, K., Dai, S., DeCesar, M. E., Demorest, P. B., Desvignes, G., Dolch, T., Drachler, B., Feng, Y., Ferrara, E. C., Fiore, W., Fonseca, E., Garver-Daniels, N., Glaser, J., Goncharov, B., Good, D. C., Griessmeier, J., Guo, Y. J., Gültekin, K., Hobbs, G., Hu, H., Islo, K., Jang, J., Jennings, R. J., Johnson, A. D., Jones, M. L., Kaczmarek, J., Kaiser, A. R., Kaplan, D. L., Keith, M., Kelley, L. Z., Kerr, M., Key, J. S., Laal, N., Lam, M. T., Lamb, W. G., Lazio, T. J. W., Liu, K., Liu, T., Luo, J., Lynch, R. S., Madison, D. R., Main, R., Manchester, R., McEwen, A., McKee, J., McLaughlin, M. A., Ng, C., Nice, D. J., Ocker, S., Olum, K. D., Osłowski, S., Pennucci, T. T., Perera, B. B. P., Perrodin, D., Porayko, N., Possenti, A., Quelquejay-Leclere, H., Ransom, S. M., Ray, P. S., Reardon, D. J., Russell, C. J., Samajdar, A., Sarkissian, J., Schult, L., Shaifullah, G., Shannon, R. M., Shapiro-Albert, B. J., Siemens, X., Simon, J. J., Siwek, M., Smith, T. L., Speri, L., Spiewak, R., Stairs, I. H., Stappers, B., Stinebring, D. R., Swiggum, J. K., Tiburzi, C., Turner, J., Vecchio, A., Verbiest, J. P. W., Wahl, H., Wang, S. Q., Wang, J., Wang, J., Wu, Z., Zhang, L., Zhang, S., and IPTA Collaboration,Jun 2023
- \aapMass measurements and 3D orbital geometry of PSR J1933-6211Geyer, M., Venkatraman Krishnan, V., Freire, P. C. C., Kramer, M., Antoniadis, J., Bailes, M., Bernadich, M. C. i., Buchner, S., Cameron, A. D., Champion, D. J., Karastergiou, A., Keith, M. J., Lower, M. E., Osłowski, S., Possenti, A., Parthasarathy, A., Reardon, D. J., Serylak, M., Shannon, R. M., Spiewak, R., van Straten, W., and Verbiest, J. P. W.Jun 2023
- VizieR Online Data CatalogVizieR Online Data Catalog: The UTMOST pulsar timing programme - II (Lower+, 2020)Lower, M. E., Bailes, M., Shannon, R. M., Johnston, S., Flynn, C., Oslowski, S., Gupta, V., Farah, W., Bateman, T., Green, A. J., Hunstead, R., Jameson, A., Jankowski, F., Parthasarathy, A., Price, D. C., Sutherland, A., Temby, D., and Venkatraman Krishnan, V.May 2023
- \mnrasThe Thousand-Pulsar-Array programme on MeerKAT - XI. Application of the rotating vector modelJohnston, S., Kramer, M., Karastergiou, A., Keith, M. J., Oswald, L. S., Parthasarathy, A., and Weltevrede, P.Apr 2023
- \mnrasThe Thousand Pulsar Array program on MeerKAT - IX. The time-averaged properties of the observed pulsar populationPosselt, B., Karastergiou, A., Johnston, S., Parthasarathy, A., Oswald, L. S., Main, R. A., Basu, A., Keith, M. J., Song, X., Weltevrede, P., Tiburzi, C., Bailes, M., Buchner, S., Geyer, M., Kramer, M., Spiewak, R., and Krishnan, V. VenkatramanApr 2023
- \mnrasThe Thousand-Pulsar-Array programme on MeerKAT - VIII. The subpulse modulation of 1198 pulsarsSong, X., Weltevrede, P., Szary, A., Wright, G., Keith, M. J., Basu, A., Johnston, S., Karastergiou, A., Main, R. A., Oswald, L. S., Parthasarathy, A., Posselt, B., Bailes, M., Buchner, S., Hugo, B., and Serylak, M.Apr 2023
- \mnrasSearches for Shapiro delay in seven binary pulsars using the MeerKAT telescopeShamohammadi, M., Bailes, M., Freire, P. C. C., Parthasarathy, A., Reardon, D. J., Shannon, R. M., Venkatraman Krishnan, V., Bernadich, M. C. i., Cameron, A. D., Champion, D. J., Corongiu, A., Flynn, C., Geyer, M., Kramer, M., Miles, M. T., Possenti, A., and Spiewak, R.Apr 2023
- \mnrasThe MeerKAT Pulsar Timing Array: first data releaseMiles, M. T., Shannon, R. M., Bailes, M., Reardon, D. J., Keith, M. J., Cameron, A. D., Parthasarathy, A., Shamohammadi, M., Spiewak, R., van Straten, W., Buchner, S., Camilo, F., Geyer, M., Karastergiou, A., Kramer, M., Serylak, M., Theureau, G., and Venkatraman Krishnan, V.Mar 2023
- \aapPSR J1910-5959A: A rare gravitational laboratory for testing white dwarf modelsCorongiu, A., Venkatraman Krishnan, V., Freire, P. C. C., Kramer, M., Possenti, A., Geyer, M., Ridolfi, A., Abbate, F., Bailes, M., Barr, E. D., Balakrishnan, V., Buchner, S., Champion, D. J., Chen, W., Hugo, B. V., Karastergiou, A., Lyne, A. G., Manchester, R. N., Padmanabh, P. V., Parthasarathy, A., Ransom, S. M., Sarkissian, J. M., Serylak, M., and van Straten, W.Mar 2023
2022
- arXiv e-printsThe Thousand-Pulsar-Array programme on MeerKAT – X. Scintillation arcs of 107 pulsarsMain, R. A., Parthasarathy, A., Johnston, S., Karastergiou, A., Basu, A., Cameron, A. D., Keith, M. J., Oswald, L. S., Posselt, B., Reardon, D. J., Song, X., and Weltevrede, P.Nov 2022
We present the detection of 107 pulsars with interstellar scintillation arcs at 856–1712 MHz, observed with the MeerKAT Thousand Pulsar Array Programme. Scintillation arcs appear to be ubiquitous in clean, high S/N observations, their detection mainly limited by short observing durations and coarse frequency channel resolution. This led the survey to be sensitive to nearby, lightly scattered pulsars with high effective velocity – from a large proper motion, a screen nearby the pulsar, or a screen near the Earth. We measure the arc curvatures in all of our sources, which can be used to give an estimate of screen distances in pulsars with known proper motion, or an estimate of the proper motion. The short scintillation timescale in J1731-4744 implies a scattering screen within 12 pc of the source, strongly suggesting the association between this pulsar and the supernova remnant RCW 114. We measure multiple parabolic arcs of 5 pulsars, all of which are weakly scintillating with high proper motion. Additionally, several sources show hints of inverted arclets suggesting scattering from anisotropic screens. Building on this work, further targeted MeerKAT observations of many of these pulsars will improve understanding of our local scattering environment and the origins of scintillation; annual scintillation curves would lead to robust screen distance measurements, and the evolution of arclets in time and frequency can constrain models of scintillation.
- arXiv e-printsA MeerKAT look at the polarization of 47 Tucanae pulsars: magnetic field implicationsAbbate, F., Possenti, A., Ridolfi, A., Venkatraman Krishnan, V., Buchner, S., Barr, E. D., Bailes, M., Kramer, M., Cameron, A., Parthasarathy, A., van Straten, W., Chen, W., Camilo, F., Padmanabh, P. V., Mao, S. A., Freire, P. C. C., Ransom, S. M., Vleeschower, L., Geyer, M., and Zhang, L.Nov 2022
We present the polarization profiles of 22 pulsars in the globular cluster 47 Tucanae using observations from the MeerKAT radio telescope at UHF-band (544-1088 MHz) and report precise values of dispersion measure (DM) and rotation measure (RM). We use these measurements to investigate the presence of turbulence in electron density and magnetic fields. The structure function of DM shows a break at ∼30 arcsec (∼0.6 pc at the distance of 47 Tucanae) that suggests the presence of turbulence in the gas in the cluster driven by the motion of wind-shedding stars. On the other hand, the structure function of RM does not show evidence of a break. This non-detection could be explained either by the limited number of pulsars or by the effects of the intervening gas in the Galaxy along the line of sight. Future pulsar discoveries in the cluster could help confirm the presence and localise the turbulence.
- arXiv e-printsGravitational signal propagation in the Double Pulsar studied with the MeerKAT telescopeHu, H., Kramer, M., Champion, D. J., Wex, N., Parthasarathy, A., Pennucci, T. T., Porayko, N. K., van Straten, W., Venkatraman Krishnan, V., Burgay, M., Freire, P. C. C., Manchester, R. N., Possenti, A., Stairs, I. H., Bailes, M., Buchner, S., Cameron, A. D., Camilo, F., and Serylak, M.Sep 2022
The Double Pulsar, PSR J0737-3039A/B, has offered a wealth of gravitational experiments in the strong-field regime, all of which GR has passed with flying colours. In particular, among current gravity experiments that test photon propagation, the Double Pulsar probes the strongest spacetime curvature. Observations with MeerKAT and, in future, the SKA can greatly improve the accuracy of current tests and facilitate tests of NLO contributions in both orbital motion and signal propagation. We present our timing analysis of new observations of PSR J0737-3039A, made using the MeerKAT telescope over the last 3 years. The increased timing precision offered by MeerKAT yields a 2 times better measurement of Shapiro delay parameter s and improved mass measurements compared to previous studies. In addition, our results provide an independent confirmation of the NLO signal propagation effects and already surpass the previous measurement from 16-yr data by a factor of 1.65. These effects include the retardation effect due to the movement of B and the deflection of the signal by the gravitational field of B. We also investigate novel effects which are expected. For instance, we search for potential profile variations near superior conjunctions caused by shifts of the line-of-sight due to latitudinal signal deflection and find insignificant evidence with our current data. With simulations, we find that the latitudinal deflection delay is unlikely to be measured with timing because of its correlation with Shapiro delay. Furthermore, although it is currently not possible to detect the expected lensing correction to the Shapiro delay, our simulations suggest that this effect may be measured with the full SKA. Finally, we provide an improved analytical description for the signal propagation in the Double Pulsar system that meets the timing precision expected from future instruments such as the full SKA.
- \aapThe eccentric millisecond pulsar, PSR J0955\ensuremath-6150. I. Pulse profile analysis, mass measurements, and constraints on binary evolutionSerylak, M., Venkatraman Krishnan, V., Freire, P. C. C., Tauris, T. M., Kramer, M., Geyer, M., Parthasarathy, A., Bailes, M., Bernadich, M. C. i., Buchner, S., Burgay, M., Camilo, F., Karastergiou, A., Lower, M. E., Possenti, A., Reardon, D. J., Shannon, R. M., Spiewak, R., Stairs, I. H., and van Straten, W.Sep 2022
Context. PSR J0955\ensuremath-6150 is a member of an enigmatic class of eccentric millisecond pulsar (MSP) and helium white dwarf (He WD) systems (eMSPs), whose binary evolution is poorly understood and believed to be strikingly different to that of traditional MSP+He WD systems in circular orbits. \Aims: Measuring the masses of the stars in this system is important for testing the different hypotheses for the formation of eMSPs. \Methods: We carried out timing observations of this pulsar with the Parkes radio telescope using the 20 cm multibeam and ultra-wide bandwidth low-frequency (UWL) receivers, and the L-band receiver of the MeerKAT radio telescope. The pulse profiles were flux and polarisation calibrated, and a rotating-vector model (RVM) was fitted to the position angle of the linear polarisation of the combined MeerKAT data. Pulse times of arrival (ToAs) were obtained from these using standard pulsar analysis techniques and analysed using the TEMPO2 timing software. \Results: Our observations reveal a strong frequency evolution of this MSP’s intensity, with a flux density spectral index (\ensuremathα) of \ensuremath-3.13(2). The improved sensitivity of MeerKAT resulted in a greater than tenfold improvement in the timing precision obtained compared to our older Parkes observations. This, combined with the eight-year timing baseline, has allowed precise measurements of a very small proper motion and three orbital post-Keplerian parameters, namely the rate of advance of periastron, \ensuremathω\ensuremath\dot = 0.00152(1) deg yr^\ensuremath-1, and the orthometric Shapiro delay parameters, h_3 = 0.89(7) \ensuremathμs and \ensuremath\varsigma = 0.88(2). Assuming general relativity, we obtain M_p = 1.71(2) M_\ensuremath⊙ for the mass of the pulsar and M_c = 0.254(2) M_\ensuremath⊙ for the mass of the companion; the orbital inclination is 83.2(4) degrees. Crucially, assuming that the position angle of the linear polarisation follows the RVM, we find that the spin axis has a misalignment relative to the orbital angular momentum of > 4.8deg at 99% confidence level. \Conclusions: While the value of M_p falls well within the wide range observed in eMSPs, M_c is significantly smaller than expected from several formation hypotheses proposed, which are therefore unlikely to be correct and can be ruled out; M_c is also significantly different from the expected value for an ideal low mass X-ray binary evolution scenario. If the misalignment between the spin axis of the pulsar and the orbital angular momentum is to be believed, it suggests that the unknown process that created the orbital eccentricity of the binary was also capable of changing its orbital orientation, an important evidence for understanding the origin of eMSPs.
- \aapTRAPUM discovery of 13 new pulsars in NGC 1851 using MeerKATRidolfi, A., Freire, P. C. C., Gautam, T., Ransom, S. M., Barr, E. D., Buchner, S., Burgay, M., Abbate, F., Venkatraman Krishnan, V., Vleeschower, L., Possenti, A., Stappers, B. W., Kramer, M., Chen, W., Padmanabh, P. V., Champion, D. J., Bailes, M., Levin, L., Keane, E. F., Breton, R. P., Bezuidenhout, M., Grießmeier, J. -M., Künkel, L., Men, Y., Camilo, F., Geyer, M., Hugo, B. V., Jameson, A., Parthasarathy, A., and Serylak, M.Aug 2022
We report the discovery of 13 new pulsars in the globular cluster NGC 1851 by the TRAPUM Large Survey Project using the MeerKAT radio telescope. The discoveries consist of six isolated millisecond pulsars (MSPs) and seven binary pulsars, of which six are MSPs and one is mildly recycled. For all the pulsars, we present the basic kinematic, astrometric, and orbital parameters, where applicable, as well as their polarimetric properties, when these are measurable. Two of the binary MSPs (PSR J0514\ensuremath-4002D and PSR J0514\ensuremath-4002E) are in wide and extremely eccentric (e > 0.7) orbits with a heavy white dwarf and a neutron star as their companion, respectively. With these discoveries, NGC 1851 is now tied with M28 as the cluster with the third largest number of known pulsars (14). Its pulsar population shows remarkable similarities with that of M28, Terzan 5, and other clusters with comparable structural parameters. The newly found pulsars are all located in the innermost regions of NGC 1851 and will likely enable, among other things, detailed studies of the cluster structure and dynamics. \\textbackslashThe data used for the pulse profiles and dynamical spectra are only available at the CDS via anonymous ftp to <A href=“http://cdsarc.u-strasbg.fr/”>cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href=“http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/664/A27”>http://cdsarc.u-strasbg.fr/viz- bin/cat/J/A+A/664/A27</A>
- MNRASDiscoveries and timing of pulsars in NGC 6440Vleeschower, L., Stappers, B. W., Bailes, M., Barr, E. D., Kramer, M., Ransom, S., Ridolfi, A., Venkatraman Krishnan, V., Possenti, A., Keith, M. J., Burgay, M., Freire, P. C. C., Spiewak, R., Champion, D. J., Bezuidenhout, M. C., Niţu, I. C., Chen, W., Parthasarathy, A., DeCesar, M. E., Buchner, S., Stairs, I. H., and Hessels, J. W. T.Jun 2022
Using the MeerKAT radio telescope, a series of observations have been conducted to time the known pulsars and search for new pulsars in the globular cluster NGC 6440. As a result, two pulsars have been discovered, NGC 6440G and NGC 6440H, one of which is isolated and the other a non-eclipsing (at frequencies above 962 MHz) ’Black Widow’, with a very low mass companion (M_c > 0.006 M_\ensuremath⊙). It joins the other binary pulsars discovered so far in this cluster that all have low companion masses (M_c < 0.30 M_\ensuremath⊙). We present the results of long-term timing solutions obtained using data from both Green Bank and MeerKAT telescopes for these two new pulsars and an analysis of the pulsars NGC 6440C and NGC 6440D. For the isolated pulsar NGC 6440C, we searched for planets using a Markov chain Monte Carlo technique. We find evidence for significant unmodelled variations but they cannot be well modelled as planets nor as part of a power-law red-noise process. Studies of the eclipses of the ’Redback’ pulsar NGC 6440D at two different frequency bands reveal a frequency dependence with longer and asymmetric eclipses at lower frequencies (962-1283 MHz).
- PASAThe MeerTime Pulsar Timing Array – A Census of Emission Properties and Timing PotentialSpiewak, R., Bailes, M., Miles, M. T., Parthasarathy, A., Reardon, D. J., Shamohammadi, M., Shannon, R. M., Bhat, N. D. R., Buchner, S., Cameron, A. D., Camilo, F., Geyer, M., Johnston, S., Karastergiou, A., Keith, M., Kramer, M., Serylak, M., van Straten, W., Theureau, G., and Venkatraman Krishnan, V.Apr 2022
MeerTime is a five-year Large Survey Project to time pulsars with MeerKAT, the 64-dish South African precursor to the Square Kilometre Array. The science goals for the programme include timing millisecond pulsars (MSPs) to high precision (< 1 \mus) to study the Galactic MSP population and to contribute to global efforts to detect nanohertz gravitational waves with the International Pulsar Timing Array (IPTA). In order to plan for the remainder of the programme and to use the allocated time most efficiently, we have conducted an initial census with the MeerKAT “L-band” receiver of 189 MSPs visible to MeerKAT and here present their dispersion measures, polarization profiles, polarization fractions, rotation measures, flux density measurements, spectral indices, and timing potential. As all of these observations are taken with the same instrument (which uses coherent dedispersion, interferometric polarization calibration techniques, and a uniform flux scale), they present an excellent resource for population studies. We used wideband pulse portraits as timing standards for each MSP and demonstrated that the MeerTime Pulsar Timing Array (MPTA) can already contribute significantly to the IPTA as it currently achieves better than 1 \mus timing accuracy on 89 MSPs (observed with fortnightly cadence). By the conclusion of the initial five-year MeerTime programme in July 2024, the MPTA will be extremely significant in global efforts to detect the gravitational wave background with a contribution to the detection statistic comparable to other long-standing timing programmes.
- ScienceA gamma-ray pulsar timing array constrains the nanohertz gravitational wave backgroundKerr, M., Parthasarathy, A., and FERMI-LAT Collaboration,Apr 2022
After large galaxies merge, their central supermassive black holes are expected to form binary systems. Their orbital motion should generate a gravitational wave background (GWB) at nanohertz frequencies. Searches for this background use pulsar timing arrays, which perform long-term monitoring of millisecond pulsars at radio wavelengths. We used 12.5 years of Fermi Large Area Telescope data to form a gamma-ray pulsar timing array. Results from 35 bright gamma-ray pulsars place a 95% credible limit on the GWB characteristic strain of 1.0 \texttimes 10^\ensuremath-14 at a frequency of 1 year^–1. The sensitivity is expected to scale with t_obs, the observing time span, as tobs\ensuremath-13/6. This direct measurement provides an independent probe of the GWB while offering a check on radio noise models.
- A&ATRAPUM discovery of thirteen new pulsars in NGC 1851 using MeerKATRidolfi, A., Freire, P. C. C., Gautam, T., Ransom, S. M., Barr, E. D., Buchner, S., Burgay, M., Abbate, F., Venkatraman Krishnan, V., Vleeschower, L., Possenti, A., Stappers, B. W., Kramer, M., Chen, W., Padmanabh, P. V., Champion, D. J., Bailes, M., Levin, L., Keane, E. F., Breton, R. P., Bezuidenhout, M., Grießmeier, J. -M., Künkel, L., Men, Y., Camilo, F., Geyer, M., Hugo, B. V., Jameson, A., Parthasarathy, A., and Serylak, M.Mar 2022
We report the discovery of 13 new pulsars in the globular cluster NGC 1851 by the TRAPUM Large Survey Project using the MeerKAT radio telescope. The discoveries consist of six isolated millisecond pulsars (MSPs) and seven binary pulsars, of which six are MSPs and one is mildly recycled. For all the pulsars, we present the basic kinematic, astrometric, and orbital parameters, where applicable, as well as their polarimetric properties, when these are measurable. Two of the binary MSPs (PSR J0514-4002D and PSR J0514-4002E) are in wide and extremely eccentric (e > 0.7) orbits with a heavy white dwarf and a neutron star as their companion, respectively. With these discoveries, NGC 1851 is now tied with M28 as the cluster with the third largest number of known pulsars (14). Its pulsar population shows remarkable similarities with that of M28, Terzan 5 and other clusters with comparable structural parameters. The newly-found pulsars are all located in the innermost regions of NGC 1851 and will likely enable, among other things, detailed studies of the cluster structure and dynamics.
- A&AThe eccentric millisecond pulsar, PSR J0955-6150 I: Pulse profile analysis, mass measurements and constraints on binary evolutionSerylak, M., Venkatraman Krishnan, V., Freire, P. C. C., Tauris, T. M., Kramer, M., Geyer, M., Parthasarathy, A., Bailes, M., Bernadich, M. C. i, Buchner, S., Burgay, M., Camilo, F., Karastergiou, A., Lower, M. E., Possenti, A., Reardon, D. J., Shannon, R. M., Spiewak, R., Stairs, I. H., and van Straten, W.Mar 2022
PSR J0955-6150 is a member of a class of eccentric MSP+He WD systems (eMSPs), whose binary evolution is poorly understood and believed to be different to that of traditional MSP+He WD systems. Measuring the masses of the stars in this system is important for testing hypotheses for the formation of eMSPs. We have carried out observations of this pulsar with the Parkes and MeerKAT radio telescopes. Our observations reveal a strong frequency evolution of this pulsar’s intensity, with a spectral index (α) of -3.13(2). The sensitivity of MeerKAT has resulted in a >10-fold improvement in the timing precision compared to older Parkes observations. Combined with the 8-year timing baseline, it has allowed precise measurements of a proper motion and three orbital “post-Keplerian” parameters: the rate of advance of periastron, \dotω = 0.00152(1) \rm deg \,yr^-1 and the orthometric Shapiro delay parameters, h_3 = 0.89(7) \mus and \varsigma = 0.88(2). Assuming general relativity, we obtain M_p = 1.71(2) M_⊙ for the mass of the pulsar and M_c = 0.254(2) M_⊙ for the mass of the companion; the orbital inclination is 83.2(4) degrees. We find that the spin axis has a misalignment relative to the orbital angular momentum of > 4.8 degrees at 99% CI. While the value of M_\rm p falls within the wide range observed in eMSPs, M_\rm c is significantly smaller than expected, allowing several formation hypotheses being ruled out. M_\rm c is also significantly different from the expected value for an ideal low mass X-ray binary evolution scenario. The putative misalignment between the spin axis of the pulsar and the orbital angular momentum suggests that the unknown process that created the orbital eccentricity of the binary was also capable of changing its orbital orientation, an important evidence for understanding the origin of eMSPs.
- MNRASThe International Pulsar Timing Array second data release: Search for an isotropic gravitational wave backgroundAntoniadis, J., Arzoumanian, Z., Babak, S., Bailes, M., Bak Nielsen, A. -S., Baker, P. T., Bassa, C. G., Bécsy, B., Berthereau, A., Bonetti, M., Brazier, A., Brook, P. R., Burgay, M., Burke-Spolaor, S., Caballero, R. N., Casey-Clyde, J. A., Chalumeau, A., Champion, D. J., Charisi, M., Chatterjee, S., Chen, S., Cognard, I., Cordes, J. M., Cornish, N. J., Crawford, F., Cromartie, H. T., Crowter, K., Dai, S., DeCesar, M. E., Demorest, P. B., Desvignes, G., Dolch, T., Drachler, B., Falxa, M., Ferrara, E. C., Fiore, W., Fonseca, E., Gair, J. R., Garver-Daniels, N., Goncharov, B., Good, D. C., Graikou, E., Guillemot, L., Guo, Y. J., Hazboun, J. S., Hobbs, G., Hu, H., Islo, K., Janssen, G. H., Jennings, R. J., Johnson, A. D., Jones, M. L., Kaiser, A. R., Kaplan, D. L., Karuppusamy, R., Keith, M. J., Kelley, L. Z., Kerr, M., Key, J. S., Kramer, M., Lam, M. T., Lamb, W. G., Lazio, T. J. W., Lee, K. J., Lentati, L., Liu, K., Luo, J., Lynch, R. S., Lyne, A. G., Madison, D. R., Main, R. A., Manchester, R. N., McEwen, A., McKee, J. W., McLaughlin, M. A., Mickaliger, M. B., Mingarelli, C. M. F., Ng, C., Nice, D. J., Osłowski, S., Parthasarathy, A., Pennucci, T. T., Perera, B. B. P., Perrodin, D., Petiteau, A., Pol, N. S., Porayko, N. K., Possenti, A., Ransom, S. M., Ray, P. S., Reardon, D. J., Russell, C. J., Samajdar, A., Sampson, L. M., Sanidas, S., Sarkissian, J. M., Schmitz, K., Schult, L., Sesana, A., Shaifullah, G., Shannon, R. M., Shapiro-Albert, B. J., Siemens, X., Simon, J., Smith, T. L., Speri, L., Spiewak, R., Stairs, I. H., Stappers, B. W., Stinebring, D. R., Swiggum, J. K., Taylor, S. R., Theureau, G., Tiburzi, C., Vallisneri, M., van der Wateren, E., Vecchio, A., Verbiest, J. P. W., Vigeland, S. J., Wahl, H., Wang, J. B., Wang, J., Wang, L., Witt, C. A., Zhang, S., and Zhu, X. J.Mar 2022
We searched for an isotropic stochastic gravitational wave background in the second data release of the International Pulsar Timing Array, a global collaboration synthesizing decadal-length pulsar-timing campaigns in North America, Europe, and Australia. In our reference search for a power-law strain spectrum of the form h_c = A(f/1 \mathrmyr^-1)^α, we found strong evidence for a spectrally similar low-frequency stochastic process of amplitude A = 3.8^+6.3_-2.5\times 10^-15 and spectral index \ensuremathα = -0.5 \ensuremath\pm 0.5, where the uncertainties represent 95 per cent credible regions, using information from the auto- and cross-correlation terms between the pulsars in the array. For a spectral index of \ensuremathα = -2/3, as expected from a population of inspiralling supermassive black hole binaries, the recovered amplitude is A = 2.8^+1.2_-0.8\times 10^-15. None the less, no significant evidence of the Hellings-Downs correlations that would indicate a gravitational- wave origin was found. We also analysed the constituent data from the individual pulsar timing arrays in a consistent way, and clearly demonstrate that the combined international data set is more sensitive. Furthermore, we demonstrate that this combined data set produces comparable constraints to recent single-array data sets which have more data than the constituent parts of the combination. Future international data releases will deliver increased sensitivity to gravitational wave radiation, and significantly increase the detection probability.
- ApJA Detection of Red Noise in PSR J1824-2452A and Projections for PSR B1937+21 Using NICER X-Ray Timing DataHazboun, Jeffrey S., Crump, Jack, Lommen, Andrea N., Montano, Sergio, Berry, Samantha J. H., Zeldes, Jesse, Teng, Elizabeth, Ray, Paul S., Kerr, Matthew, Arzoumanian, Zaven, Bogdanov, Slavko, Deneva, Julia, Lewandowska, Natalia, Markwardt, Craig B., Ransom, Scott, Enoto, Teruaki, Wood, Kent S., Gendreau, Keith C., Howe, David A., and Parthasarathy, AdityaMar 2022
We have used X-ray data from the Neutron Star Interior Composition Explorer (NICER) to search for long-timescale temporal correlations (“red noise”) in the pulse times of arrival (TOAs) from the millisecond pulsars PSR J1824-2452A and PSR B1937+21. These data more closely track intrinsic noise because X-rays are unaffected by the radio-frequency-dependent propagation effects of the interstellar medium. Our search yields strong evidence (natural log Bayes factor of 9.634 \ensuremath\pm 0.016) for red noise in PSR J1824-2452A, but the search is inconclusive for PSR B1937+21. In the interest of future X-ray missions, we devise and implement a method to simulate longer and higher-precision X-ray data sets to determine the timing baseline necessary to detect red noise. We find that the red noise in PSR B1937+21 can be reliably detected in a 5 yr mission with a TOA error of 2 \ensuremathμs and an observing cadence of 20 observations per month compared to the 5 \ensuremathμs TOA error and 11 observations per month that NICER currently achieves in PSR B1937+21. We investigate detecting red noise in PSR B1937+21 with other combinations of observing cadences and TOA errors. We also find that time-correlated red noise commensurate with an injected stochastic gravitational-wave background having an amplitude of A _GWB = 2 \texttimes 10^-15 and spectral index of timing residuals of \ensuremathγ _GWB = 13/3 can be detected in a pulsar with similar TOA precision to PSR B1937+21. This is with no additional red noise in a 10 yr mission that observes the pulsar 15 times per month and has an average TOA error of 1 \ensuremathμs.
- PhyRevRHigh-precision search for dark photon dark matter with the Parkes Pulsar Timing ArrayXue, Xiao, Xia, Zi-Qing, Zhu, Xingjiang, Zhao, Yue, Shu, Jing, Yuan, Qiang, Bhat, N. D. Ramesh, Cameron, Andrew D., Dai, Shi, Feng, Yi, Goncharov, Boris, Hobbs, George, Howard, Eric, Manchester, Richard N., Parthasarathy, Aditya, Reardon, Daniel J., Russell, Christopher J., Shannon, Ryan M., Spiewak, Renée, Thyagarajan, Nithyanandan, Wang, Jingbo, Zhang, Lei, Zhang, Songbo, and PPTA Collaboration,Feb 2022
The nature of dark matter remains obscure in spite of decades of experimental efforts. The mass of dark matter candidates can span a wide range, and its coupling with the Standard Model sector remains uncertain. All these unknowns make the detection of dark matter extremely challenging. Ultralight dark matter, with m \ensuremath∼10^\ensuremath-22 eV, is proposed to reconcile the disagreements between observations and predictions from simulations of small-scale structures in the cold dark matter paradigm while remaining consistent with other observations. Because of its large de Broglie wavelength and large local occupation number within galaxies, ultralight dark matter behaves like a coherently oscillating background field with an oscillating frequency dependent on its mass. If the dark matter particle is a spin-1 dark photon, such as the U (1_) B or U (1_) B \ensuremath-L gauge boson, it can induce an external oscillating force and lead to displacements of test masses. Such an effect would be observable in the form of periodic variations in the arrival times of radio pulses from highly stable millisecond pulsars. In this study, we search for evidence of ultralight dark photon dark matter (DPDM) using 14-year high-precision observations of 26 pulsars collected with the Parkes Pulsar Timing Array. While no statistically significant signal is found, we place constraints on coupling constants for the U (1_) B and U (1_) B \ensuremath-L DPDM. Compared with other experiments, the limits on the dimensionless coupling constant \ensuremath\varepsilon achieved in our study are improved by up to two orders of magnitude when the dark photon mass is smaller than 3 \texttimes10^\ensuremath-22 eV (10^\ensuremath-22 eV) for the U (1_) B (U (1_) B \ensuremath-L ) scenario.
- MNRASNoise analysis in the European Pulsar Timing Array data release 2 and its implications on the gravitational-wave background searchChalumeau, A., Babak, S., Petiteau, A., Chen, S., Samajdar, A., Caballero, R. N., Theureau, G., Guillemot, L., Desvignes, G., Parthasarathy, A., Liu, K., Shaifullah, G., Hu, H., van der Wateren, E., Antoniadis, J., Bak Nielsen, A. -S., Bassa, C. G., Berthereau, A., Burgay, M., Champion, D. J., Cognard, I., Falxa, M., Ferdman, R. D., Freire, P. C. C., Gair, J. R., Graikou, E., Guo, Y. J., Jang, J., Janssen, G. H., Karuppusamy, R., Keith, M. J., Kramer, M., Lee, K. J., Liu, X. J., Lyne, A. G., Main, R. A., McKee, J. W., Mickaliger, M. B., Perera, B. B. P., Perrodin, D., Porayko, N. K., Possenti, A., Sanidas, S. A., Sesana, A., Speri, L., Stappers, B. W., Tiburzi, C., Vecchio, A., Verbiest, J. P. W., Wang, J., Wang, L., and Xu, H.Feb 2022
The European Pulsar Timing Array (EPTA) collaboration has recently released an extended data set for six pulsars (DR2) and reported evidence for a common red noise signal. Here we present a noise analysis for each of the six pulsars. We consider several types of noise: (i) radio frequency independent, ’achromatic’, and time-correlated red noise; (ii) variations of dispersion measure and scattering; (iii) system and band noise; and (iv) deterministic signals (other than gravitational waves) that could be present in the PTA data. We perform Bayesian model selection to find the optimal combination of noise components for each pulsar. Using these custom models we revisit the presence of the common uncorrelated red noise signal previously reported in the EPTA DR2 and show that the data still supports it with a high statistical significance. Next, we confirm that there is no preference for or against the Hellings-Downs spatial correlations expected for the stochastic gravitational-wave background. The main conclusion of the EPTA DR2 paper remains unchanged despite a very significant change in the noise model of each pulsar. However, modelling the noise is essential for the robust detection of gravitational waves and its impact could be significant when analysing the next EPTA data release, which will include a larger number of pulsars and more precise measurements.
- MNRASThe thousand-pulsar-array programme on MeerKAT VII: polarisation properties of pulsars in the Magellanic CloudsJohnston, S., Parthasarathy, A., Main, R. A., Ridley, J. P., Koribalski, B. S., Bailes, M., Buchner, S. J., Geyer, M., Karastergiou, A., Keith, M. J., Kramer, M., Serylak, M., Shannon, R. M., Spiewak, R., and Krishnan, V. VenkatramanFeb 2022
The Magellanic Clouds are the only external galaxies known to host radio pulsars. The dispersion and rotation measures of pulsars in the Clouds can aid in understanding their structure, and studies of the pulsars themselves can point to potential differences between them and their Galactic counterparts. We use the high sensitivity of the MeerKAT telescope to observe 17 pulsars in the Small and Large Magellanic Clouds in addition to five foreground (Galactic) pulsars. We provide polarisation profiles for 18 of these pulsars, improved measurements of their dispersion and rotation measures, and derive the mean parallel magnetic field along the lines of sight. The results are broadly in agreement with expectations for the structure and strength of the magnetic field in the Large and Small Magellanic Clouds. The Magellanic Cloud pulsars have profiles which are narrower than expected from the period-width relationship and we show this is due to selection effects in pulsar surveys rather than any intrinsic difference between the population of Galactic and Magellanic objects.
2021
- MNRASCommon-red-signal analysis with 24-yr high-precision timing of the European Pulsar Timing Array: inferences in the stochastic gravitational-wave background searchChen, S., Caballero, R. N., Guo, Y. J., Chalumeau, A., Liu, K., Shaifullah, G., Lee, K. J., Babak, S., Desvignes, G., Parthasarathy, A., Hu, H., van der Wateren, E., Antoniadis, J., Bak Nielsen, A. -S., Bassa, C. G., Berthereau, A., Burgay, M., Champion, D. J., Cognard, I., Falxa, M., Ferdman, R. D., Freire, P. C. C., Gair, J. R., Graikou, E., Guillemot, L., Jang, J., Janssen, G. H., Karuppusamy, R., Keith, M. J., Kramer, M., Liu, X. J., Lyne, A. G., Main, R. A., McKee, J. W., Mickaliger, M. B., Perera, B. B. P., Perrodin, D., Petiteau, A., Porayko, N. K., Possenti, A., Samajdar, A., Sanidas, S. A., Sesana, A., Speri, L., Stappers, B. W., Theureau, G., Tiburzi, C., Vecchio, A., Verbiest, J. P. W., Wang, J., Wang, L., and Xu, H.Dec 2021
We present results from the search for a stochastic gravitational-wave background (GWB) as predicted by the theory of General Relativity using six radio millisecond pulsars from the Data Release 2 (DR2) of the European Pulsar Timing Array (EPTA) covering a timespan up to 24 yr. A GWB manifests itself as a long-term low-frequency stochastic signal common to all pulsars, a common red signal (CRS), with the characteristic Hellings- Downs (HD) spatial correlation. Our analysis is performed with two independent pipelines, ENTERPRISE, and TEMPONEST+FORTYTWO, which produce consistent results. A search for a CRS with simultaneous estimation of its spatial correlations yields spectral properties compatible with theoretical GWB predictions, but does not result in the required measurement of the HD correlation, as required for GWB detection. Further Bayesian model comparison between different types of CRSs, including a GWB, finds the most favoured model to be the common uncorrelated red noise described by a power law with A = 5.13_-2.73^+4.20 \times 10^-15 and γ= 3.78_-0.59^+0.69 (95 per cent credible regions). Fixing the spectral index to \ensuremathγ = 13/3 as expected from the GWB by circular, inspiralling supermassive black hole binaries results in an amplitude of A =2.95_-0.72^+0.89 \times 10^-15. We implement three different models, BAYESEPHEM, LINIMOSS, and EPHEMGP, to address possible Solar system ephemeris (SSE) systematics and conclude that our results may only marginally depend on these effects. This work builds on the methods and models from the studies on the EPTA DR1. We show that under the same analysis framework the results remain consistent after the data set extension.
- MNRASThe Thousand-Pulsar-Array programme on MeerKAT - VI. Pulse widths of a large and diverse sample of radio pulsarsPosselt, B., Karastergiou, A., Johnston, S., Parthasarathy, A., Keith, M. J., Oswald, L. S., Song, X., Weltevrede, P., Barr, E. D., Buchner, S., Geyer, M., Kramer, M., Reardon, D. J., Serylak, M., Shannon, R. M., Spiewak, R., and Venkatraman Krishnan, V.Dec 2021
We present pulse width measurements for a sample of radio pulsars observed with the MeerKAT telescope as part of the Thousand- Pulsar-Array (TPA) programme in the MeerTime project. For a centre frequency of 1284 MHz, we obtain 762 W_10 measurements across the total bandwidth of 775 MHz, where W_10 is the width at the 10 per cent level of the pulse peak. We also measure about 400 W_10 values in each of the four or eight frequency sub-bands. Assuming, the width is a function of the rotation period P, this relationship can be described with a power law with power law index \ensuremathμ = -0.29 \ensuremath\pm 0.03. However, using orthogonal distance regression, we determine a steeper power law with \ensuremathμ = -0.63 \ensuremath\pm 0.06. A density plot of the period-width data reveals such a fit to align well with the contours of highest density. Building on a previous population synthesis model, we obtain population- based estimates of the obliquity of the magnetic axis with respect to the rotation axis for our pulsars. Investigating the width changes over frequency, we unambiguously identify a group of pulsars that have width broadening at higher frequencies. The measured width changes show a monotonic behaviour with frequency for the whole TPA pulsar population, whether the pulses are becoming narrower or broader with increasing frequency. We exclude a sensitivity bias, scattering and noticeable differences in the pulse component numbers as explanations for these width changes, and attempt an explanation using a qualitative model of five contributing Gaussian pulse components with flux density spectra that depend on their rotational phase.
- MNRASThe impact of glitches on young pulsar rotational evolutionLower, M. E., Johnston, S., Dunn, L., Shannon, R. M., Bailes, M., Dai, S., Kerr, M., Manchester, R. N., Melatos, A., Oswald, L. S., Parthasarathy, A., Sobey, C., and Weltevrede, P.Dec 2021
We report on a timing programme of 74 young pulsars that have been observed by the Parkes 64-m radio telescope over the past decade. Using modern Bayesian timing techniques, we have measured the properties of 124 glitches in 52 of these pulsars, of which 74 are new. We demonstrate that the glitch sample is complete to fractional increases in spin frequency greater than ∆ν^90 \rm per cent_\mathrm g/ν≈8.1 \times 10^-9 . We measure values of the braking index, n, in 33 pulsars. In most of these pulsars, their rotational evolution is dominated by episodes of spin-down with n > 10, punctuated by step changes in the spin-down rate at the time of a large glitch. The step changes are such that, averaged over the glitches, the long-term n is small. We find a near one-to- one relationship between the interglitch value of n and the change in spin-down of the previous glitch divided by the interglitch time interval. We discuss the results in the context of a range of physical models.
- ApJlThe Radius of PSR J0740+6620 from NICER and XMM-Newton DataMiller, M. C., Lamb, F. K., Dittmann, A. J., Bogdanov, S., Arzoumanian, Z., Gendreau, K. C., Guillot, S., Ho, W. C. G., Lattimer, J. M., Loewenstein, M., Morsink, S. M., Ray, P. S., Wolff, M. T., Baker, C. L., Cazeau, T., Manthripragada, S., Markwardt, C. B., Okajima, T., Pollard, S., Cognard, I., Cromartie, H. T., Fonseca, E., Guillemot, L., Kerr, M., Parthasarathy, A., Pennucci, T. T., Ransom, S., and Stairs, I.Sep 2021
PSR J0740+6620 has a gravitational mass of 2.08 \ensuremath\pm 0.07 M_\ensuremath⊙, which is the highest reliably determined mass of any neutron star. As a result, a measurement of its radius will provide unique insight into the properties of neutron star core matter at high densities. Here we report a radius measurement based on fits of rotating hot spot patterns to Neutron Star Interior Composition Explorer (NICER) and X-ray Multi-Mirror (XMM-Newton) X-ray observations. We find that the equatorial circumferential radius of PSR J0740+6620 is 13.7_-1.5^+2.6 km (68%). We apply our measurement, combined with the previous NICER mass and radius measurement of PSR J0030+0451, the masses of two other \raisebox-0.5ex\textasciitilde2 M_\ensuremath⊙ pulsars, and the tidal deformability constraints from two gravitational wave events, to three different frameworks for equation-of-state modeling, and find consistent results at \raisebox-0.5ex\textasciitilde1.5-5 times nuclear saturation density. For a given framework, when all measurements are included, the radius of a 1.4 M_\ensuremath⊙ neutron star is known to \ensuremath\pm4% (68% credibility) and the radius of a 2.08 M_\ensuremath⊙ neutron star is known to \ensuremath\pm5%. The full radius range that spans the \ensuremath\pm1\ensuremathσ credible intervals of all the radius estimates in the three frameworks is 12.45 \ensuremath\pm 0.65 km for a 1.4 M_\ensuremath⊙ neutron star and 12.35 \ensuremath\pm 0.75 km for a 2.08 M_\ensuremath⊙ neutron star.
- ApJlA NICER View of the Massive Pulsar PSR J0740+6620 Informed by Radio Timing and XMM-Newton SpectroscopyRiley, Thomas E., Watts, Anna L., Ray, Paul S., Bogdanov, Slavko, Guillot, Sebastien, Morsink, Sharon M., Bilous, Anna V., Arzoumanian, Zaven, Choudhury, Devarshi, Deneva, Julia S., Gendreau, Keith C., Harding, Alice K., Ho, Wynn C. G., Lattimer, James M., Loewenstein, Michael, Ludlam, Renee M., Markwardt, Craig B., Okajima, Takashi, Prescod-Weinstein, Chanda, Remillard, Ronald A., Wolff, Michael T., Fonseca, Emmanuel, Cromartie, H. Thankful, Kerr, Matthew, Pennucci, Timothy T., Parthasarathy, Aditya, Ransom, Scott, Stairs, Ingrid, Guillemot, Lucas, and Cognard, IsmaelSep 2021
We report on Bayesian estimation of the radius, mass, and hot surface regions of the massive millisecond pulsar PSR J0740+6620, conditional on pulse-profile modeling of Neutron Star Interior Composition Explorer X-ray Timing Instrument event data. We condition on informative pulsar mass, distance, and orbital inclination priors derived from the joint North American Nanohertz Observatory for Gravitational Waves and Canadian Hydrogen Intensity Mapping Experiment/Pulsar wideband radio timing measurements of Fonseca et al. We use XMM-Newton European Photon Imaging Camera spectroscopic event data to inform our X-ray likelihood function. The prior support of the pulsar radius is truncated at 16 km to ensure coverage of current dense matter models. We assume conservative priors on instrument calibration uncertainty. We constrain the equatorial radius and mass of PSR J0740+6620 to be 12.39_-0.98^+1.30 km and 2.072_-0.066^+0.067 M_\ensuremath⊙ respectively, each reported as the posterior credible interval bounded by the 16% and 84% quantiles, conditional on surface hot regions that are non-overlapping spherical caps of fully ionized hydrogen atmosphere with uniform effective temperature; a posteriori, the temperature is \mathrmlog_10(T\,[\rmK])=5.99_-0.06^+0.05 for each hot region. All software for the X-ray modeling framework is open-source and all data, model, and sample information is publicly available, including analysis notebooks and model modules in the Python language. Our marginal likelihood function of mass and equatorial radius is proportional to the marginal joint posterior density of those parameters (within the prior support) and can thus be computed from the posterior samples.
- MNRASThe thousand-pulsar-array programme on MeerKAT IV: Polarization properties of young, energetic pulsarsSerylak, M., Johnston, S., Kramer, M., Buchner, S., Karastergiou, A., Keith, M. J., Parthasarathy, A., Weltevrede, P., Bailes, M., Barr, E. D., Camilo, F., Geyer, M., Hugo, B. V., Jameson, A., Reardon, D. J., Shannon, R. M., Spiewak, R., van Straten, W., and Venkatraman Krishnan, V.Aug 2021
We present observations of 35 high spin-down energy radio pulsars using the MeerKAT telescope. Polarization profiles and associated parameters are also presented. We derive the geometry for a selection of pulsars which show interpulse emission. We point out that, in several cases, these radio pulsars should also be seen in \ensuremathγ-rays but that improved radio timing is required to aid the high-energy detection. We discuss the relationship between the width of the radio profile and its high-energy detectability. Finally, we reflect on the correlation between the spin-down energy and the radio polarization fraction and the implications this may have for \ensuremathγ-ray emission.
- MNRASThe Thousand-Pulsar-Array programme on MeerKAT - II. Observing strategy for pulsar monitoring with subarraysSong, X., Weltevrede, P., Keith, M. J., Johnston, S., Karastergiou, A., Bailes, M., Barr, E. D., Buchner, S., Geyer, M., Hugo, B. V., Jameson, A., Parthasarathy, A., Reardon, D. J., Serylak, M., Shannon, R. M., Spiewak, R., van Straten, W., and Venkatraman Krishnan, V.Aug 2021
The Thousand-Pulsar-Array (TPA) programme currently monitors about 500 pulsars with the sensitive MeerKAT radio telescope by using subarrays to observe multiple sources simultaneously. Here we define the adopted observing strategy, which guarantees that each target is observed long enough to obtain a high-fidelity pulse profile, thereby reaching a sufficient precision of a simple pulse shape parameter. This precision is estimated from the contribution of the system noise of the telescope, and the pulse-to-pulse variability of each pulsar, which we quantify under some simplifying assumptions. We test the assumptions and choice of model parameters using data from the MeerKAT 64-dish array and the Lovell and Parkes telescopes. We demonstrate that the observing times derived from our method produce high- fidelity pulse profiles that meet the needs of the TPA in studying pulse shape variability and pulsar timing. Our method can also be used to compare strategies for observing large numbers of pulsars with telescopes capable of forming multiple subarray configurations. We find that using two 32-dish MeerKAT subarrays is the most efficient strategy for the TPA project. We also find that the ability to observe in different array configurations will become increasingly important for large observing programmes using the Square Kilometre Array telescope.
- ApJlOn the Evidence for a Common-spectrum Process in the Search for the Nanohertz Gravitational-wave Background with the Parkes Pulsar Timing ArrayGoncharov, Boris, Shannon, R. M., Reardon, D. J., Hobbs, G., Zic, A., Bailes, M., Curyło, M., Dai, S., Kerr, M., Lower, M. E., Manchester, R. N., Mandow, R., Middleton, H., Miles, M. T., Parthasarathy, A., Thrane, E., Thyagarajan, N., Xue, X., Zhu, X. -J., Cameron, A. D., Feng, Y., Luo, R., Russell, C. J., Sarkissian, J., Spiewak, R., Wang, S., Wang, J. B., Zhang, L., and Zhang, S.Aug 2021
A nanohertz-frequency stochastic gravitational-wave background can potentially be detected through the precise timing of an array of millisecond pulsars. This background produces low-frequency noise in the pulse arrival times that would have a characteristic spectrum common to all pulsars and a well-defined spatial correlation. Recently the North American Nanohertz Observatory for Gravitational Waves collaboration (NANOGrav) found evidence for the common-spectrum component in their 12.5 yr data set. Here we report on a search for the background using the second data release of the Parkes Pulsar Timing Array. If we are forced to choose between the two NANOGrav models-one with a common-spectrum process and one without-we find strong support for the common-spectrum process. However, in this paper, we consider the possibility that the analysis suffers from model misspecification. In particular, we present simulated data sets that contain noise with distinctive spectra but show strong evidence for a common-spectrum process under the standard assumptions. The Parkes data show no significant evidence for, or against, the spatially correlated Hellings-Downs signature of the gravitational-wave background. Assuming we did observe the process underlying the spatially uncorrelated component of the background, we infer its amplitude to be A=2.2_-0.3^+0.4\times 10^-15 in units of gravitational-wave strain at a frequency of 1 yr^-1. Extensions and combinations of existing and new data sets will improve the prospects of identifying spatial correlations that are necessary to claim a detection of the gravitational-wave background.
- ApJlRefined Mass and Geometric Measurements of the High-mass PSR J0740+6620Fonseca, E., Cromartie, H. T., Pennucci, T. T., Ray, P. S., Kirichenko, A. Yu., Ransom, S. M., Demorest, P. B., Stairs, I. H., Arzoumanian, Z., Guillemot, L., Parthasarathy, A., Kerr, M., Cognard, I., Baker, P. T., Blumer, H., Brook, P. R., DeCesar, M., Dolch, T., Dong, F. A., Ferrara, E. C., Fiore, W., Garver-Daniels, N., Good, D. C., Jennings, R., Jones, M. L., Kaspi, V. M., Lam, M. T., Lorimer, D. R., Luo, J., McEwen, A., McKee, J. W., McLaughlin, M. A., McMann, N., Meyers, B. W., Naidu, A., Ng, C., Nice, D. J., Pol, N., Radovan, H. A., Shapiro-Albert, B., Tan, C. M., Tendulkar, S. P., Swiggum, J. K., Wahl, H. M., and Zhu, W. W.Jul 2021
We report results from continued timing observations of PSR J0740+6620, a high-mass, 2.8 ms radio pulsar in orbit with a likely ultracool white dwarf companion. Our data set consists of combined pulse arrival-time measurements made with the 100 m Green Bank Telescope and the Canadian Hydrogen Intensity Mapping Experiment telescope. We explore the significance of timing- based phenomena arising from general relativistic dynamics and variations in pulse dispersion. When using various statistical methods, we find that combining \raisebox-0.5ex\textasciitilde1.5 yr of additional, high- cadence timing data with previous measurements confirms and improves on previous estimates of relativistic effects within the PSR J0740+6620 system, with the pulsar mass m_p=\,2.08_-0.07^+0.07 M_⊙ (68.3% credibility) determined by the relativistic Shapiro time delay. For the first time, we measure secular variation in the orbital period and argue that this effect arises from apparent acceleration due to significant transverse motion. After incorporating contributions from Galactic differential rotation and off-plane acceleration in the Galactic potential, we obtain a model-dependent distance of d\,=\,1.14_-0.15^+0.17 kpc (68.3% credibility). This improved distance confirms the ultracool nature of the white dwarf companion determined from recent optical observations. We discuss the prospects for future observations with next-generation facilities, which will likely improve the precision on m_p for J0740+6620 by an order of magnitude within the next few years.
- MNRASThe relativistic binary programme on MeerKAT: science objectives and first resultsKramer, M., Stairs, I. H., Venkatraman Krishnan, V., Freire, P. C. C., Abbate, F., Bailes, M., Burgay, M., Buchner, S., Champion, D. J., Cognard, I., Gautam, T., Geyer, M., Guillemot, L., Hu, H., Janssen, G., Lower, M. E., Parthasarathy, A., Possenti, A., Ransom, S., Reardon, D. J., Ridolfi, A., Serylak, M., Shannon, R. M., Spiewak, R., Theureau, G., van Straten, W., Wex, N., Oswald, L. S., Posselt, B., Sobey, C., Barr, E. D., Camilo, F., Hugo, B., Jameson, A., Johnston, S., Karastergiou, A., Keith, M., and Osłowski, S.Jun 2021
We describe the ongoing Relativistic Binary programme (RelBin), a part of the MeerTime large survey project with the MeerKAT radio telescope. RelBin is primarily focused on observations of relativistic effects in binary pulsars to enable measurements of neutron star masses and tests of theories of gravity. We selected 25 pulsars as an initial high priority list of targets based on their characteristics and observational history with other telescopes. In this paper, we provide an outline of the programme, and present polarization calibrated pulse profiles for all selected pulsars as a reference catalogue along with updated dispersion measures. We report Faraday rotation measures for 24 pulsars, twelve of which have been measured for the first time. More than a third of our selected pulsars show a flat position angle swing confirming earlier observations. We demonstrate the ability of the Rotating Vector Model, fitted here to seven binary pulsars, including the Double Pulsar (PSR J0737-3039A), to obtain information about the orbital inclination angle. We present a high time resolution light curve of the eclipse of PSR J0737-3039A by the companion’s magnetosphere, a high-phase-resolution position angle swing for PSR J1141-6545, an improved detection of the Shapiro delay of PSR J1811-2405, and pulse scattering measurements for PSRs J1227-6208, J1757-1854, and J1811-1736. Finally, we demonstrate that timing observations with MeerKAT improve on existing data sets by a factor of, typically, 2-3, sometimes by an order of magnitude.
- MNRASEight new millisecond pulsars from the first MeerKAT globular cluster censusRidolfi, A., Gautam, T., Freire, P. C. C., Ransom, S. M., Buchner, S. J., Possenti, A., Venkatraman Krishnan, V., Bailes, M., Kramer, M., Stappers, B. W., Abbate, F., Barr, E. D., Burgay, M., Camilo, F., Corongiu, A., Jameson, A., Padmanabh, P. V., Vleeschower, L., Champion, D. J., Chen, W., Geyer, M., Karastergiou, A., Karuppusamy, R., Parthasarathy, A., Reardon, D. J., Serylak, M., Shannon, R. M., and Spiewak, R.Jun 2021
We have used the central 44 antennas of the new 64-dish MeerKAT radio telescope array to conduct a deep search for new pulsars in the core of nine globular clusters (GCs). This has led to the discovery of eight new millisecond pulsars in six different clusters. Two new binaries, 47 Tuc ac and 47 Tuc ad, are eclipsing ’spiders’, featuring compact orbits (\ensuremath≲0.32 d), very low mass companions, and regular occultations of their pulsed emission. The other three new binary pulsars (NGC 6624G, M62G, and Ter 5 an) are in wider (>0.7 d) orbits, with companions that are likely to be white dwarfs or neutron stars. NGC 6624G has a large eccentricity of e ≃ 0.38, which enabled us to detect the rate of advance of periastron. This suggests that the system is massive, with a total mass of M_tot = 2.65 \ensuremath\pm 0.07 M_\ensuremath⊙. Likewise, for Ter 5 an, with e ≃ 0.0066, we obtain M_tot = 2.97 \ensuremath\pm 0.52 M_\ensuremath⊙. The other three new discoveries (NGC 6522D, NGC 6624H, and NGC 6752F) are faint isolated pulsars. Finally, we have used the whole MeerKAT array and synthesized 288 beams, covering an area of \raisebox-0.5ex\textasciitilde2 arcmin in radius around the centre of NGC 6624. This has allowed us to localize many of the pulsars in the cluster, demonstrating the beamforming capabilities of the TRAPUM software backend and paving the way for the upcoming MeerKAT GC pulsar survey.
- MNRASThe Thousand-Pulsar-Array programme on MeerKAT - V. Scattering analysis of single-component pulsarsOswald, L. S., Karastergiou, A., Posselt, B., Johnston, S., Bailes, M., Buchner, S., Geyer, M., Keith, M. J., Kramer, M., Parthasarathy, A., Reardon, D. J., Serylak, M., Shannon, R. M., Spiewak, R., van Straten, W., and Venkatraman Krishnan, V.Jun 2021
We have measured the scattering time-scale, \ensuremathτ, and the scattering spectral index, \ensuremathα, for 84 single- component pulsars. Observations were carried out with the MeerKAT telescope as part of the Thousand-Pulsar-Array programme in the MeerTime project at frequencies between 0.895 and 1.670 GHz. Our results give a distribution of values for \ensuremathα (defined in terms of \ensuremathτ and frequency \ensuremathν as \ensuremathτ \ensuremath∝ \ensuremathν^-\ensuremathα) for which, upon fitting a Gaussian, we obtain a mean and standard deviation of <\ensuremathα> = 4.0 \ensuremath\pm 0.6. This is due to our identification of possible causes of inaccurate measurement of \ensuremathτ, which, if not filtered out of modelling results, tend to lead to underestimation of \ensuremathα. The pulsars in our sample have large dispersion measures and are therefore likely to be distant. We find that a model using an isotropic scatter broadening function is consistent with the data, likely due to the averaging effect of multiple scattering screens along the line of sight. Our sample of scattering parameters provides a strong data set upon which we can build to test more complex and time-dependent scattering phenomena, such as extreme scattering events.
- MNRASA polarization census of bright pulsars using the ultrawideband receiver on the Parkes radio telescopeSobey, C., Johnston, S., Dai, S., Kerr, M., Manchester, R. N., Oswald, L. S., Parthasarathy, A., Shannon, R. M., and Weltevrede, P.Jun 2021
We present high signal-to-noise ratio, full polarization pulse profiles for 40 bright, ’slowly’ rotating (non-recycled) pulsars using the new ultrawideband low-frequency (UWL; 704-4032 MHz) receiver on the Parkes radio telescope. We obtain updated and accurate interstellar medium parameters towards these pulsars (dispersion measures and Faraday rotation measures), and reveal Faraday dispersion towards PSR J1721-3532 caused by interstellar scattering. We find general trends in the pulse profiles including decreasing fractional linear polarization and increasing degree of circular polarization with increasing frequency, consistent with previous studies, while also revealing new features and frequency evolution. This demonstrates results that can be obtained using UWL monitoring observations of slow pulsars, which are valuable for improving our understanding of pulsar emission and the intervening interstellar medium. The calibrated data products are publicly available.
- MNRASMultifrequency observations of SGR J1935+2154Bailes, M., Bassa, C. G., Bernardi, G., Buchner, S., Burgay, M., Caleb, M., Cooper, A. J., Desvignes, G., Groot, P. J., Heywood, I., Jankowski, F., Karuppusamy, R., Kramer, M., Malenta, M., Naldi, G., Pilia, M., Pupillo, G., Rajwade, K. M., Spitler, L., Surnis, M., Stappers, B. W., Addis, A., Bloemen, S., Bezuidenhout, M. C., Bianchi, G., Champion, D. J., Chen, W., Driessen, L. N., Geyer, M., Gourdji, K., Hessels, J. W. T., Kondratiev, V. I., Klein-Wolt, M., Körding, E., Le Poole, R., Liu, K., Lower, M. E., Lyne, A. G., Magro, A., McBride, V., Mickaliger, M. B., Morello, V., Parthasarathy, A., Paterson, K., Perera, B. B. P., Pieterse, D. L. A., Pleunis, Z., Possenti, A., Rowlinson, A., Serylak, M., Setti, G., Tavani, M., Wijers, R. A. M. J., ter Veen, S., Venkatraman Krishnan, V., Vreeswijk, P., and Woudt, P. A.Jun 2021
Magnetars are a promising candidate for the origin of fast radio bursts (FRBs). The detection of an extremely luminous radio burst from the Galactic magnetar SGR J1935+2154 on 2020 April 28 added credence to this hypothesis. We report on simultaneous and non- simultaneous observing campaigns using the Arecibo, Effelsberg, LOFAR, MeerKAT, MK2, and Northern Cross radio telescopes and the MeerLICHT optical telescope in the days and months after the April 28 event. We did not detect any significant single radio pulses down to fluence limits between 25 mJy ms and 18 Jy ms. Some observing epochs overlapped with times when X-ray bursts were detected. Radio images made on 4 d using the MeerKAT telescope revealed no point-like persistent or transient emission at the location of the magnetar. No transient or persistent optical emission was detected over seven days. Using the multicolour MeerLICHT images combined with relations between DM, N_H, and reddening, we constrain the distance to SGR J1935+2154, to be between 1.5 and 6.5 kpc. The upper limit is consistent with some other distance indicators and suggests that the April 28 burst is closer to two orders of magnitude less energetic than the least energetic FRBs. The lack of single- pulse radio detections shows that the single pulses detected over a range of fluences are either rare, or highly clustered, or both. It may also indicate that the magnetar lies somewhere between being radio-quiet and radio-loud in terms of its ability to produce radio emission efficiently.
- MNRASTwo years of pulsar observations with the ultra-wide-band receiver on the Parkes radio telescopeJohnston, Simon, Sobey, C., Dai, S., Keith, M., Kerr, M., Manchester, R. N., Oswald, L. S., Parthasarathy, A., Shannon, R. M., and Weltevrede, P.Mar 2021
The major programme for observing young, non-recycled pulsars with the Parkes telescope has transitioned from a narrow-band system to an ultra-wide-band system capable of observing between 704 and 4032 MHz. We report here on the initial 2 yr of observations with this receiver. Results include dispersion measure (DM) and Faraday rotation measure (RM) variability with time, determined with higher precision than hitherto, flux density measurements and the discovery of several nulling and mode changing pulsars. PSR J1703-4851 is shown to be one of a small subclass of pulsars that has a weak and a strong mode which alternate rapidly in time. PSR J1114-6100 has the fourth highest |RM| of any known pulsar despite its location far from the Galactic Centre. PSR J1825-1446 shows variations in both DM and RM likely due to its motion behind a foreground supernova remnant.
- MNRASIdentifying and mitigating noise sources in precision pulsar timing data setsGoncharov, Boris, Reardon, D. J., Shannon, R. M., Zhu, Xing-Jiang, Thrane, Eric, Bailes, M., Bhat, N. D. R., Dai, S., Hobbs, G., Kerr, M., Manchester, R. N., Osłowski, S., Parthasarathy, A., Russell, C. J., Spiewak, R., Thyagarajan, N., and Wang, J. B.Mar 2021
Pulsar timing array projects measure the pulse arrival times of millisecond pulsars for the primary purpose of detecting nanohertz-frequency gravitational waves. The measurements include contributions from a number of astrophysical and instrumental processes, which can either be deterministic or stochastic. It is necessary to develop robust statistical and physical models for these noise processes because incorrect models diminish sensitivity and may cause a spurious gravitational wave detection. Here we characterize noise processes for the 26 pulsars in the second data release of the Parkes Pulsar Timing Array using Bayesian inference. In addition to well-studied noise sources found previously in pulsar timing array data sets such as achromatic timing noise and dispersion measure variations, we identify new noise sources including time-correlated chromatic noise that we attribute to variations in pulse scattering. We also identify ’exponential dip’ events in four pulsars, which we attribute to magnetospheric effects as evidenced by pulse profile shape changes observed for three of the pulsars. This includes an event in PSR J1713+0747, which had previously been attributed to interstellar propagation. We present noise models to be used in searches for gravitational waves. We outline a robust methodology to evaluate the performance of noise models and identify unknown signals in the data. The detection of variations in pulse profiles highlights the need to develop efficient profile domain timing methods.
- MNRASMeasurements of pulse jitter and single-pulse variability in millisecond pulsars using MeerKATParthasarathy, A., Bailes, M., Shannon, R. M., van Straten, W., Osłowski, S., Johnston, S., Spiewak, R., Reardon, D. J., Kramer, M., Venkatraman Krishnan, V., Pennucci, T. T., Abbate, F., Buchner, S., Camilo, F., Champion, D. J., Geyer, M., Hugo, B., Jameson, A., Karastergiou, A., Keith, M. J., and Serylak, M.Mar 2021
Using the state-of-the-art SKA precursor, the MeerKAT radio telescope, we explore the limits to precision pulsar timing of millisecond pulsars achievable due to pulse stochasticity (jitter). We report new jitter measurements in 15 of the 29 pulsars in our sample and find that the levels of jitter can vary dramatically between them. For some, like the 2.2 ms pulsar PSR J2241-5236, we measure an implied jitter of just \raisebox-0.5ex\textasciitilde4 ns h^-1, while others, like the 3.9 ms PSR J0636-3044, are limited to \raisebox-0.5ex\textasciitilde100 ns h^-1. While it is well known that jitter plays a central role to limiting the precision measurements of arrival times for high signal-to-noise ratio observations, its role in the measurement of dispersion measure (DM) has not been reported, particularly in broad-band observations. Using the exceptional sensitivity of MeerKAT, we explored this on the bright millisecond pulsar PSR J0437-4715 by exploring the DM of literally every pulse. We found that the derived single-pulse DMs vary by typically 0.0085 cm^-3 pc from the mean, and that the best DM estimate is limited by the differential pulse jitter across the band. We postulate that all millisecond pulsars will have their own limit on DM precision which can only be overcome with longer integrations. Using high- time resolution filterbank data of 9 \ensuremathμs, we also present a statistical analysis of single-pulse phenomenology. Finally, we discuss optimization strategies for the MeerKAT pulsar timing program and its role in the context of the International Pulsar Timing Array.
- Pulse-to-Pulse Intensity Modulation of Three X-Ray Pulsars Using NICER DataLevina, S., Tygh, M., Lommen, A., Lewandowska, N., Wood, K., Parthasarathy, A., and Nicer Timing Working Group,Jan 2021
We studied the X-ray emissions of the pulsars PSR B1937+21, PSR B1821-24, and the Crab pulsar (PSR B0531+21) using the Neutron star Interior Composition Explorer (NICER). We are looking for evidence of non-Gaussian modulation in the intensity of the pulses in order to study their emission mechanisms by conducting a pulse-to-pulse analysis. For PSR B1937+21 and PSR B1821-24 this is the first time that a pulse-by-pulse study has been done in the X-ray regime. We have observed that the pulsars PSR B1937+21 and PSR B1821-24 adhere to a Gaussian distribution of pulse intensities, while the Crab pulsar deviates from a Gaussian distribution.
2020
- ApJPrecision Orbital Dynamics from Interstellar Scintillation Arcs for PSR J0437-4715Reardon, Daniel J., Coles, William A., Bailes, Matthew, Bhat, N. D. Ramesh, Dai, Shi, Hobbs, George B., Kerr, Matthew, Manchester, Richard N., Osłowski, Stefan, Parthasarathy, Aditya, Russell, Christopher J., Shannon, Ryan M., Spiewak, Renée, Toomey, Lawrence, Tuntsov, Artem V., van Straten, Willem, Walker, Mark A., Wang, Jingbo, Zhang, Lei, and Zhu, Xing-JiangDec 2020
Intensity scintillations of radio pulsars are known to originate from interference between waves scattered by the electron density irregularities of interstellar plasma, often leading to parabolic arcs in the two-dimensional power spectrum of the recorded dynamic spectrum. The degree of arc curvature depends on the distance to the scattering plasma and its transverse velocity with respect to the line of sight. We report the observation of annual and orbital variations in the curvature of scintillation arcs over a period of 16 yr for the bright millisecond pulsar, PSR J0437-4715. These variations are the signature of the relative transverse motions of Earth, the pulsar, and the scattering medium, which we model to obtain precise measurements of parameters of the pulsar’s binary orbit and the scattering medium itself. We observe two clear scintillation arcs in most of our >5000 observations, and we show that they originate from scattering by thin screens located at distances D_1 = 89.8 \ensuremath\pm 0.4 pc and D_2 = 124 \ensuremath\pm 3 pc from Earth. The best-fit scattering model we derive for the brightest arc yields the pulsar’s orbital inclination angle, i = 137\textdegree1 \ensuremath\pm 0\textdegree3, and longitude of ascending node, \ensuremathΩ = 206\textdegree3 \ensuremath\pm 0\textdegree4. Using scintillation arcs for precise astrometry and orbital dynamics can be superior to modeling variations in the diffractive scintillation timescale, because the arc curvature is independent of variations in the level of turbulence of interstellar plasma. This technique can be used in combination with pulsar timing to determine the full three-dimensional orbital geometries of binary pulsars and provides parameters essential for testing theories of gravity and constraining neutron star masses.
- MNRASHigh-cadence observations and variable spin behaviour of magnetar Swift J1818.0-1607 after its outburstChampion, David, Cognard, Ismael, Cruces, Marilyn, Desvignes, Gregory, Jankowski, Fabian, Karuppusamy, Ramesh, Keith, Michael J., Kouveliotou, Chryssa, Kramer, Michael, Liu, Kuo, Lyne, Andrew G., Mickaliger, Mitchell B., O’Connor, Brendan, Parthasarathy, Aditya, Porayko, Nataliya, Rajwade, Kaustubh, Stappers, Ben W., Torne, Pablo, van der Horst, Alexander J., and Weltevrede, PatrickNov 2020
We report on multifrequency radio observations of the new magnetar Swift J1818.0-1607, following it for more than one month with high cadence. The observations commenced less than 35 h after its registered first outburst. We obtained timing, polarization, and spectral information. Swift J1818.0-1607 has an unusually steep spectrum for a radio emitting magnetar and also has a relatively narrow and simple pulse profile. The position angle swing of the polarization is flat over the pulse profile, possibly suggesting that our line of sight grazes the edge of the emission beam. This may also explain the steep spectrum. The spin evolution shows large variation in the spin-down rate, associated with four distinct timing events over the course of our observations. Those events may be related to the appearance and disappearance of a second pulse component. The first timing event coincides with our actual observations, while we did not detect significant changes in the emission properties that could reveal further magnetospheric changes. Characteristic ages inferred from the timing measurements over the course of months vary by nearly an order of magnitude. A longer-term spin-down measurement over approximately 100 d suggests a characteristic age of about 500 yr, larger than previously reported. Though Swift J1818.0-1607 could still be one of the youngest neutron stars (and magnetars) detected so far, we caution using the characteristic age as a true-age indicator given the caveats behind its calculation.
- PASAThe MeerKAT telescope as a pulsar facility: System verification and early science results from MeerTimeBailes, M., Jameson, A., Abbate, F., Barr, E. D., Bhat, N. D. R., Bondonneau, L., Burgay, M., Buchner, S. J., Camilo, F., Champion, D. J., Cognard, I., Demorest, P. B., Freire, P. C. C., Gautam, T., Geyer, M., Griessmeier, J. -M., Guillemot, L., Hu, H., Jankowski, F., Johnston, S., Karastergiou, A., Karuppusamy, R., Kaur, D., Keith, M. J., Kramer, M., van Leeuwen, J., Lower, M. E., Maan, Y., McLaughlin, M. A., Meyers, B. W., Osłowski, S., Oswald, L. S., Parthasarathy, A., Pennucci, T., Posselt, B., Possenti, A., Ransom, S. M., Reardon, D. J., Ridolfi, A., Schollar, C. T. G., Serylak, M., Shaifullah, G., Shamohammadi, M., Shannon, R. M., Sobey, C., Song, X., Spiewak, R., Stairs, I. H., Stappers, B. W., van Straten, W., Szary, A., Theureau, G., Venkatraman Krishnan, V., Weltevrede, P., Wex, N., Abbott, T. D., Adams, G. B., Burger, J. P., Gamatham, R. R. G., Gouws, M., Horn, D. M., Hugo, B., Joubert, A. F., Manley, J. R., McAlpine, K., Passmoor, S. S., Peens-Hough, A., Ramudzuli, Z. R., Rust, A., Salie, S., Schwardt, L. C., Siebrits, R., Van Tonder, G., Van Tonder, V., and Welz, M. G.Jul 2020
We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for the newly commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. MeerKAT is a high-gain ( ∼2.8 \mboxK Jy^-1 ) low-system temperature ( ∼18 \mboxK at 20 \mboxcm ) radio array that currently operates at 580-1 670 MHz and can produce tied- array beams suitable for pulsar observations. This paper presents results from the MeerTime Large Survey Project and commissioning tests with PTUSE. Highlights include observations of the double pulsar \mboxJ0737-3039\mboxA , pulse profiles from 34 millisecond pulsars (MSPs) from a single 2.5-h observation of the Globular cluster Terzan 5, the rotation measure of Ter5O, a 420-sigma giant pulse from the Large Magellanic Cloud pulsar PSR \mboxJ0540-6919 , and nulling identified in the slow pulsar PSR J0633-2015. One of the key design specifications for MeerKAT was absolute timing errors of less than 5 ns using their novel precise time system. Our timing of two bright MSPs confirm that MeerKAT delivers exceptional timing. PSR \mboxJ2241-5236 exhibits a jitter limit of <4 \mboxns h^-1 whilst timing of PSR \mboxJ1909-3744 over almost 11 months yields an rms residual of 66 ns with only 4 min integrations. Our results confirm that the MeerKAT is an exceptional pulsar telescope. The array can be split into four separate sub-arrays to time over 1 000 pulsars per day and the future deployment of S-band (1 750-3 500 MHz) receivers will further enhance its capabilities.
- PASAThe Parkes Pulsar Timing Array project: second data releaseKerr, Matthew, Reardon, Daniel J., Hobbs, George, Shannon, Ryan M., Manchester, Richard N., Dai, Shi, Russell, Christopher J., Zhang, Songbo, van Straten, Willem, Osłowski, Stefan, Parthasarathy, Aditya, Spiewak, Renee, Bailes, Matthew, Bhat, N. D. Ramesh, Cameron, Andrew D., Coles, William A., Dempsey, James, Deng, Xinping, Goncharov, Boris, Kaczmarek, Jane F., Keith, Michael J., Lasky, Paul D., Lower, Marcus E., Preisig, Brett, Sarkissian, John Mihran, Toomey, Lawrence, Wang, Hongguang, Wang, Jingbo, Zhang, Lei, and Zhu, XingjiangJun 2020
We describe 14 yr of public data from the Parkes Pulsar Timing Array (PPTA), an ongoing project that is producing precise measurements of pulse times of arrival from 26 millisecond pulsars using the 64-m Parkes radio telescope with a cadence of approximately 3 weeks in three observing bands. A comprehensive description of the pulsar observing systems employed at the telescope since 2004 is provided, including the calibration methodology and an analysis of the stability of system components. We attempt to provide full accounting of the reduction from the raw measured Stokes parameters to pulse times of arrival to aid third parties in reproducing our results. This conversion is encapsulated in a processing pipeline designed to track provenance. Our data products include pulse times of arrival for each of the pulsars along with an initial set of pulsar parameters and noise models. The calibrated pulse profiles and timing template profiles are also available. These data represent almost 21 000 h of recorded data spanning over 14 yr. After accounting for processes that induce time-correlated noise, 22 of the pulsars have weighted root-mean-square timing residuals of <\!\!1 μs in at least one radio band. The data should allow end users to quickly undertake their own gravitational wave analyses, for example, without having to understand the intricacies of pulsar polarisation calibration or attain a mastery of radio frequency interference mitigation as is required when analysing raw data files.
- ATELResurgence in the radio flux of the magnetar XTE J1810-197Lower, M. E., Gupta, V., Flynn, C., Bailes, M., Jameson, A., Farah, W., Bateman, T., Campbell-Wilson, D., Day, C. K., Deller, A., Green, A. J., Mandlik, A., Oslowski, S., Parthasarathy, A., Price, D. C., Sutherland, A., Temby, D., Torr, G., Urquhart, G., Krishnan, V. Venkatraman, and Venville, T.Jun 2020
Following its radio revival in late-2018 (Levin et al. 2019) we have performed regular timing observations of the magnetar XTE J1810-197 with the Molonglo Observatory Synthesis Telescope as part of the UTMOST project (Bailes et al. 2017).
- ATELFRB200607 found by UTMOSTGupta, V., Bailes, M., Jameson, A., Flynn, C., Farah, W., Bateman, T., Campbell-Wilson, D., Day, C., Deller, A., Green, A. J., Hunstead, R. W., Mandlik, A., Lower, M. E., Oslowski, S., Parthasarathy, A., Price, D. C., Sutherland, A., Temby, D., Torr, G., Urquhart, G., and Krishnan, V. VenkatramanJun 2020
At UTC 2020-06-07-10:37:21.7 (2020-06-07.442612269), we found a fast radio burst as part of the ongoing search program at the Molonglo telescope (UTMOST). Molonglo is a 1.6 km long East-West array (Bailes et al 2017, PASA, 34, 45) and was operating in drift-scan mode, pointing at the meridian at the time of detection.
- MNRASTiming of young radio pulsars - II. Braking indices and their interpretationParthasarathy, A., Johnston, S., Shannon, R. M., Lentati, L., Bailes, M., Dai, S., Kerr, M., Manchester, R. N., Osłowski, S., Sobey, C., van Straten, W., and Weltevrede, P.May 2020
In Paper I of this series, we detected a significant value of the braking index (n) for 19 young, high- \dotE radio pulsars using \ensuremath∼10 yr of timing observations from the 64-m Parkes radio telescope. Here, we investigate this result in more detail using a Bayesian pulsar timing framework to model timing noise and to perform selection to distinguish between models containing exponential glitch recovery and braking index signatures. We show that consistent values of n are maintained with the addition of substantial archival data, even in the presence of glitches. We provide strong arguments that our measurements are unlikely due to exponential recovery signals from unseen glitches even though glitches play a key role in the evolution of a pulsar’s spin frequency. We conclude that, at least over decadal time-scales, the value of n can be significantly larger than the canonical 3 and discuss the implications for the evolution of pulsars.
- MNRASThe UTMOST pulsar timing programme - II. Timing noise across the pulsar populationLower, M. E., Bailes, M., Shannon, R. M., Johnston, S., Flynn, C., Osłowski, S., Gupta, V., Farah, W., Bateman, T., Green, A. J., Hunstead, R., Jameson, A., Jankowski, F., Parthasarathy, A., Price, D. C., Sutherland, A., Temby, D., and Venkatraman Krishnan, V.May 2020
While pulsars possess exceptional rotational stability, large-scale timing studies have revealed at least two distinct types of irregularities in their rotation: red timing noise and glitches. Using modern Bayesian techniques, we investigated the timing noise properties of 300 bright southern-sky radio pulsars that have been observed over 1.0-4.8 yr by the upgraded Molonglo Observatory Synthesis Telescope (MOST). We reanalysed the spin and spin-down changes associated with nine previously reported pulsar glitches, report the discovery of three new glitches and four unusual glitch-like events in the rotational evolution of PSR J1825-0935. We develop a refined Bayesian framework for determining how red noise strength scales with pulsar spin frequency (\ensuremathν) and spin-down frequency ( \dotν ), which we apply to a sample of 280 non-recycled pulsars. With this new method and a simple power-law scaling relation, we show that red noise strength scales across the non- recycled pulsar population as ν^a |\dotν|^b , where a = -0.84^+0.47_-0.49 and b = 0.97^+0.16_-0.19 . This method can be easily adapted to utilize more complex, astrophysically motivated red noise models. Lastly, we highlight our timing of the double neutron star PSR J0737-3039, and the rediscovery of a bright radio pulsar originally found during the first Molonglo pulsar surveys with an incorrectly catalogued position.
- ATELFRB 200508 found by UTMOSTGupta, V., Bailes, M., Jameson, A., Flynn, C., Farah, W., Bateman, T., Campbell-Wilson, D., Day, C., Deller, A., Green, A. J., Hunstead, R. W., Mandlik, A., Lower, M. E., Oslowski, S., Parthasarathy, A., Price, D. C., Sutherland, A., Temby, D., Torr, G., Urquhart, G., and Krishnan, V. VenkatramanMay 2020
At UTC 2020-05-08-07:42:09.5 (2020-05-08.320943), we found a fast radio burst as part of the ongoing search program at the Molonglo telescope (UTMOST). Molonglo is a 1.6 km long East-West array (Bailes et al 2017, PASA, 34, 45) and was operating in drift- scan mode, pointing at the meridian at the time of detection.
- MNRASThe Thousand-Pulsar-Array programme on MeerKAT - I. Science objectives and first resultsJohnston, Simon, Karastergiou, A., Keith, M. J., Song, X., Weltevrede, P., Abbate, F., Bailes, M., Buchner, S., Camilo, F., Geyer, M., Hugo, B., Jameson, A., Kramer, M., Parthasarathy, A., Reardon, D. J., Ridolfi, A., Serylak, M., Shannon, R. M., Spiewak, R., van Straten, W., Venkatraman Krishnan, V., Jankowski, F., Meyers, B. W., Oswald, L., Posselt, B., Sobey, C., Szary, A., and van Leeuwen, J.Apr 2020
We report here on initial results from the Thousand-Pulsar-Array (TPA) programme, part of the Large Survey Project ’MeerTime’ on the MeerKAT telescope. The interferometer is used in the tied-array mode in the band from 856 to 1712 MHz, and the wide band coupled with the large collecting area and low receiver temperature make it an excellent telescope for the study of radio pulsars. The TPA is a 5 year project, which aims at to observing (a) more than 1000 pulsars to obtain high-fidelity pulse profiles, (b) some 500 of these pulsars over multiple epochs, and (c) long sequences of single-pulse trains from several hundred pulsars. The scientific outcomes from the programme will include the determination of pulsar geometries, the location of the radio emission within the pulsar magnetosphere, the connection between the magnetosphere and the crust and core of the star, tighter constraints on the nature of the radio emission itself, as well as interstellar medium studies. First, results presented here include updated dispersion measures, 26 pulsars with Faraday rotation measures derived for the first time, and a description of interesting emission phenomena observed thus far.
- MNRASThe UTMOST survey for magnetars, intermittent pulsars, RRATs, and FRBs - I. System description and overviewVenkatraman Krishnan, V., Flynn, C., Farah, W., Jameson, A., Bailes, M., Osłowski, S., Bateman, T., Gupta, V., van Straten, W., Keane, E. F., Barr, E. D., Bhandari, S., Caleb, M., Campbell-Wilson, D., Day, C. K., Deller, A., Green, A. J., Hunstead, R., Jankowski, F., Lower, M. E., Parthasarathy, A., Plant, K., Price, D. C., Rosado, P. A., and Temby, D.Mar 2020
We describe the ongoing ‘survey for magnetars, intermittent pulsars, rotating radio transients, and fast radio bursts’ (SMIRF), performed using the newly refurbished UTMOST telescope. SMIRF repeatedly sweeps the southern Galactic plane performing real- time periodicity and single pulse searches, and is the first survey of its kind carried out with an interferometer. SMIRF is facilitated by a robotic scheduler which is capable of fully autonomous commensal operations. We report on the SMIRF observational parameters, the data analysis methods, the survey’s sensitivity to pulsars, techniques to mitigate radio frequency interference, and present some early survey results. UTMOST’s wide field of view permits a full sweep of the Galactic plane to be performed every fortnight, two orders of magnitude faster than previous surveys. In six months of operations from 2018 January to June, we have performed \ensuremath∼10 sweeps of the Galactic plane with SMIRF. Notable blind redetections include the magnetar PSR J1622-4950, the RRAT PSR J0941-3942 and the eclipsing pulsar PSR J1748-2446A. We also report the discovery of a new pulsar, PSR J1659-54. Our follow- up of this pulsar at an average flux limit of \ensuremath≤20 mJy, categorizes this as an intermittent pulsar with a high nulling fraction of <0.002.
- ATELMeerKAT observation of the radio magnetar candidate Swift J1818.0-1607Lower, Marcus E., Buchner, Sarah, Johnston, Simon, Parthasarathy, Aditya, Geyer, Marisa, and Bailes, MatthewMar 2020
Following the reported detection and confirmation of pulsed radio emission from the magnetar candidate Swift J1818.0-1607 (GCN #27373; ATel #13553; ATel #13554), we conducted a 15 minute observation of the pulsar with the MeerKAT array at UTC 2020-03-16-09:31 as part of the MeerTime thousand-pulsar-array project (Johnston et al. 2020).
- VizieR CatalogVizieR Online Data Catalog: UTMOST pulsar timing programme. I. (Jankowski+, 2019)Jankowski, F., Bailes, M., van Straten, W., Keane, E. F., Flynn, C., Barr, E. D., Bateman, T., Bhandari, S., Caleb, M., Campbell-Wilson, D., Farah, W., Green, A. J., Hunstead, R. W., Jameson, A., Oslowski, S., Parthasarathy, A., Rosado, P. A., and Venkatraman Krishnan, V.Feb 2020
We present updated astrometric ephemerides and rotational parameters for 205 radio pulsars, of which 8 are in binary systems, and 197 are isolated. For 60 of them, we publish inferred proper motions and transverse velocities, and for all of them, we report band- integrated flux densities, modulation indices and pulse widths at 50 and 10 per cent maximum at a frequency of 843 MHz. Our measurements are based on up to daily observations with time spans of 1.4 to 3yr performed at the refurbished Molonglo Observatory Synthesis Radio Telescope (MOST), a radio interferometer located in Australia. \\textbackslashIn table 3, we list the pulsar names (J2000), the proper motions in right ascension and declination, proper motion measurements from the literature where available, the maximum time spans between position measurements, the number of positions in the fit, the references for the literature proper motions, the pulsar distances and their transverse velocities. \\textbackslashIn table B1, we report the pulsar names (J2000), their positions referenced to the ICRF, their spin frequencies and first temporal derivatives, the root mean square timing residuals in us and as a fractions of the pulsar periods, the number of pulse arrival times, the reduced chi2 and degrees of freedom of the fits, the timing baselines and a flag whether we corrected the pulse arrival times for underestimation. Table B1 shows the results for 8 pulsars in binary systems. Table B2 reports the results for 197 isolated pulsars, in a format analogue to the one of table B1. \\textbackslashIn table C1, names (J2000), whether they have interpulses, their band-integrated flux densities at 843MHz, their robust modulation indices and their pulse widths at 50 and 10 per cent maximum. The period, position and dispersion measure determination epoch is set to MJD 57600 for all pulsars. We report all uncertainties at the 1 sigma level. \\(4 data files).
- MNRASProbing the extragalactic fast transient sky at minute time-scales with DECamAndreoni, I., Cooke, J., Webb, S., Rest, A., Pritchard, T., Caleb, M., Chang, S. -W., Farah, W., Lien, A., Möller, A., Ravasio, M. E., Abbott, T. M. C., Bhandari, S., Cucchiara, A., Flynn, C., Jankowski, F., Keane, E. F., Moriya, T. J., Onken, C. A., Parthasarathy, A., Price, D. C., Petroff, E., Ryder, S., Vohl, D., and Wolf, C.Feb 2020
Searches for optical transients are usually performed with a cadence of days to weeks, optimized for supernova discovery. The optical fast transient sky is still largely unexplored, with only a few surveys to date having placed meaningful constraints on the detection of extragalactic transients evolving at sub-hour time- scales. Here, we present the results of deep searches for dim, minute-time-scale extragalactic fast transients using the Dark Energy Camera, a core facility of our all-wavelength and all- messenger Deeper, Wider, Faster programme. We used continuous 20 s exposures to systematically probe time-scales down to 1.17 min at magnitude limits g > 23 (AB), detecting hundreds of transient and variable sources. Nine candidates passed our strict criteria on duration and non-stellarity, all of which could be classified as flare stars based on deep multiband imaging. Searches for fast radio burst and gamma-ray counterparts during simultaneous multifacility observations yielded no counterparts to the optical transients. Also, no long-term variability was detected with pre-imaging and follow-up observations using the SkyMapper optical telescope. We place upper limits for minute-time-scale fast optical transient rates for a range of depths and time- scales. Finally, we demonstrate that optical g-band light-curve behaviour alone cannot discriminate between confirmed extragalactic fast transients such as prompt GRB flashes and Galactic stellar flares.
2019
- Notes of AASDetection of a Glitch in PSR J0908-4913 by UTMOSTLower, Marcus E., Bailes, Matthew, Shannon, Ryan M., Johnston, Simon, Flynn, Chris, Bateman, Timothy, Campbell-Wilson, Duncan, Day, Cherie K., Deller, Adam, Farah, Wael, Green, Anne J., Gupta, Vivek, Hunstead, Richard W., Jameson, Andrew, Mandlik, Ayushi, Osłowski, Stefan, Parthasarathy, Aditya, Price, Daniel C., Sutherland, Angus, Temby, David, Torr, Glen, Urquhart, Glenn, and Venkatraman Krishnan, VivekDec 2019
We report the first detection of a glitch in the radio pulsar PSR J0908-4913 (PSR B0906-49) during regular timing observations by the Molonglo Observatory Synthesis Telescope (MOST) as part of the UTMOST project.
- MNRASThe International Pulsar Timing Array: second data releasePerera, B. B. P., DeCesar, M. E., Demorest, P. B., Kerr, M., Lentati, L., Nice, D. J., Osłowski, S., Ransom, S. M., Keith, M. J., Arzoumanian, Z., Bailes, M., Baker, P. T., Bassa, C. G., Bhat, N. D. R., Brazier, A., Burgay, M., Burke-Spolaor, S., Caballero, R. N., Champion, D. J., Chatterjee, S., Chen, S., Cognard, I., Cordes, J. M., Crowter, K., Dai, S., Desvignes, G., Dolch, T., Ferdman, R. D., Ferrara, E. C., Fonseca, E., Goldstein, J. M., Graikou, E., Guillemot, L., Hazboun, J. S., Hobbs, G., Hu, H., Islo, K., Janssen, G. H., Karuppusamy, R., Kramer, M., Lam, M. T., Lee, K. J., Liu, K., Luo, J., Lyne, A. G., Manchester, R. N., McKee, J. W., McLaughlin, M. A., Mingarelli, C. M. F., Parthasarathy, A. P., Pennucci, T. T., Perrodin, D., Possenti, A., Reardon, D. J., Russell, C. J., Sanidas, S. A., Sesana, A., Shaifullah, G., Shannon, R. M., Siemens, X., Simon, J., Spiewak, R., Stairs, I. H., Stappers, B. W., Swiggum, J. K., Taylor, S. R., Theureau, G., Tiburzi, C., Vallisneri, M., Vecchio, A., Wang, J. B., Zhang, S. B., Zhang, L., Zhu, W. W., and Zhu, X. J.Dec 2019
In this paper, we describe the International Pulsar Timing Array second data release, which includes recent pulsar timing data obtained by three regional consortia: the European Pulsar Timing Array, the North American Nanohertz Observatory for Gravitational Waves, and the Parkes Pulsar Timing Array. We analyse and where possible combine high-precision timing data for 65 millisecond pulsars which are regularly observed by these groups. A basic noise analysis, including the processes which are both correlated and uncorrelated in time, provides noise models and timing ephemerides for the pulsars. We find that the timing precisions of pulsars are generally improved compared to the previous data release, mainly due to the addition of new data in the combination. The main purpose of this work is to create the most up-to-date IPTA data release. These data are publicly available for searches for low-frequency gravitational waves and other pulsar science.
- ATELFRB191223 found at UTMOSTGupta, V., Bailes, M., Jameson, A., Flynn, C., Farah, W., Bateman, T., Campbell-Wilson, D., Day, C., Deller, A., Green, A. J., Hunstead, R. W., Mandlik, A., Lower, M. E., Oslowski, S., Parthasarathy, A., Price, D. C., Sutherland, A., Temby, D., Torr, G., Urquhart, G., and Krishnan, V. VenkatramanDec 2019
At UTC 2019-12-23-04:55:31.2 (2019-12-23.205222222), we found a fast radio burst as part of the ongoing search program at the Molonglo telescope (UTMOST). Molonglo is a 1.6 km long East-West array (Bailes et al 2017, PASA, 34, 45) and was operating in drift-scan mode, pointing at the meridian at the time of detection.
- MNRASTiming of young radio pulsars - I. Timing noise, periodic modulation, and proper motionParthasarathy, A., Shannon, R. M., Johnston, S., Lentati, L., Bailes, M., Dai, S., Kerr, M., Manchester, R. N., Osłowski, S., Sobey, C., van Straten, W., and Weltevrede, P.Nov 2019
The smooth spin-down of young pulsars is perturbed by two non- deterministic phenomenon, glitches, and timing noise. Although the timing noise provides insights into nuclear and plasma physics at extreme densities, it acts as a barrier to high- precision pulsar timing experiments. An improved methodology based on the Bayesian inference is developed to simultaneously model the stochastic and deterministic parameters for a sample of 85 high-\textbackslashdot{E} radio pulsars observed for \ensuremath∼10 yr with the 64-m Parkes radio telescope. Timing noise is known to be a red process and we develop a parametrization based on the red-noise amplitude (A_red) and spectral index (\ensuremathβ). We measure the median A_red to be -10.4\^{+1.8}_{-1.7} yr^3/2 and \ensuremathβ to be -5.2\^{+3.0}_{-3.8} and show that the strength of timing noise scales proportionally to \ensuremathν ^1|\textbackslashdot{\ensuremathν }|\^{-0.6\ensuremath\pm 0.1}, where \ensuremathν is the spin frequency of the pulsar and \textbackslashdot{\ensuremathν } is its spin-down rate. Finally, we measure significant braking indices for 19 pulsars and proper motions for 2 pulsars, and discuss the presence of periodic modulation in the arrival times of 5 pulsars.
- ATELFRB190711 found at UTMOSTGupta, V., Bailes, M., Jameson, A., Flynn, C., Farah, W., Bateman, T., Campbell-Wilson, D., Day, C., Deller, A., Green, A. J., Hunstead, R. W., Mandlik, A., Lower, M. E., Oslowski, S., Parthasarathy, A., Price, D. C., Sutherland, A., Temby, D., Torr, G., Urquhart, G., and Krishnan, V. VenkatramanNov 2019
At UTC 2019-11-07-18:55:36.7 (2019-11-07.788619213), we found a fast radio burst as part of the ongoing search program (UTMOST), at the Molonglo telescope.
- MNRASFive new real-time detections of fast radio bursts with UTMOSTFarah, W., Flynn, C., Bailes, M., Jameson, A., Bateman, T., Campbell-Wilson, D., Day, C. K., Deller, A. T., Green, A. J., Gupta, V., Hunstead, R., Lower, M. E., Osłowski, S., Parthasarathy, A., Price, D. C., Ravi, V., Shannon, R. M., Sutherland, A., Temby, D., Krishnan, V. Venkatraman, Caleb, M., Chang, S. -W., Cruces, M., Roy, J., Morello, V., Onken, C. A., Stappers, B. W., Webb, S., and Wolf, C.Sep 2019
We detail a new fast radio burst (FRB) survey with the Molonglo Radio Telescope, in which six FRBs were detected between 2017 June and 2018 December. By using a real-time FRB detection system, we captured raw voltages for five of the six events, which allowed for coherent dedispersion and very high time resolution (10.24 \ensuremathμs) studies of the bursts. Five of the FRBs show temporal broadening consistent with interstellar and/or intergalactic scattering, with scattering time-scales ranging from 0.16 to 29.1 ms. One burst, FRB181017, shows remarkable temporal structure, with three peaks each separated by 1 ms. We searched for phase-coherence between the leading and trailing peaks and found none, ruling out lensing scenarios. Based on this survey, we calculate an all-sky rate at 843 MHz of 98\^{+59}_{-39} events sky^-1 d^-1 to a fluence limit of 8 Jy ms: a factor of 7 below the rates estimated from the Parkes and ASKAP telescopes at 1.4 GHz assuming the ASKAP- derived spectral index \ensuremathα = -1.6 (F_\ensuremathν \ensuremath∝ \ensuremathν^\ensuremathα). Our results suggest that FRB spectra may turn over below 1 GHz. Optical, radio, and X-ray follow-up has been made for most of the reported bursts, with no associated transients found. No repeat bursts were found in the survey.
- MNRASCommensal discovery of four fast radio bursts during Parkes Pulsar Timing Array observationsOsłowski, S., Shannon, R. M., Ravi, V., Kaczmarek, J. F., Zhang, S., Hobbs, G., Bailes, M., Russell, C. J., van Straten, W., James, C. W., Jameson, A., Mahony, E. K., Kumar, P., Andreoni, I., Bhat, N. D. R., Burke-Spolaor, S., Dai, S., Dempsey, J., Kerr, M., Manchester, R. N., Parthasarathy, A., Reardon, D., Sarkissian, J. M., Spiewak, R., Toomey, L., Wang, J. -B., Zhang, L., and Zhu, X. -J.Sep 2019
The Parkes Pulsar Timing Array (PPTA) project monitors two dozen millisecond pulsars (MSPs) in order to undertake a variety of fundamental physics experiments using the Parkes 64-m radio telescope. Since 2017 June, we have been undertaking commensal searches for fast radio bursts (FRBs) during the MSP observations. Here, we report the discovery of four FRBs (171209, 180309, 180311, and 180714). The detected events include an FRB with the highest signal-to-noise ratio ever detected at the Parkes Observatory, which exhibits unusual spectral properties. All four FRBs are highly polarized. We discuss the future of commensal searches for FRBs at Parkes.
- ASCLMolsoft: Molonglo Telescope Observing SoftwareJankowski, Fabian, Parthasarathy, Aditya, Farah, Wael, and Flynn, ChrisAug 2019
- ATELFRB190806 found at UTMOSTGupta, V., Bailes, M., Jameson, A., Flynn, C., Farah, W., Bateman, T., Campbell-Wilson, D., Day, C., Deller, A., Green, A. J., Hunstead, R. W., Lower, M. E., Oslowski, S., Parthasarathy, A., Price, D. C., Sutherland, A., Temby, D., Torr, G., Urquhart, G., and Krishnan, V. VenkatramanAug 2019
At UTC 2019-08-06-17:07:58.0 (2019-08-06.7138657407), we found a fast radio burst as part of the ongoing search program (UTMOST), at the Molonglo telescope.
- MNRASThe UTMOST pulsar timing programme I: Overview and first resultsJankowski, F., Bailes, M., van Straten, W., Keane, E. F., Flynn, C., Barr, E. D., Bateman, T., Bhandari, S., Caleb, M., Campbell-Wilson, D., Farah, W., Green, A. J., Hunstead, R. W., Jameson, A., Osłowski, S., Parthasarathy, A., Rosado, P. A., and Venkatraman Krishnan, V.Apr 2019
We present an overview and the first results from a large-scale pulsar timing programme that is part of the UTMOST project at the refurbished Molonglo Observatory Synthesis Radio Telescope (MOST) near Canberra, Australia. We currently observe more than 400 mainly bright southern radio pulsars with up to daily cadences. For 205 (8 in binaries, 4 millisecond pulsars), we publish updated timing models, together with their flux densities, flux density variability, and pulse widths at 843 MHz, derived from observations spanning between 1.4 and 3 yr. In comparison with the ATNF pulsar catalogue, we improve the precision of the rotational and astrometric parameters for 123 pulsars, for 47 by at least an order of magnitude. The time spans between our measurements and those in the literature are up to 48 yr, which allow us to investigate their long-term spin- down history and to estimate proper motions for 60 pulsars, of which 24 are newly determined and most are major improvements. The results are consistent with interferometric measurements from the literature. A model with two Gaussian components centred at 139 and 463 km s^-1 fits the transverse velocity distribution best. The pulse duty cycle distributions at 50 and 10 per cent maximum are best described by lognormal distributions with medians of 2.3 and 4.4 per cent, respectively. We discuss two pulsars that exhibit spin-down rate changes and drifting subpulses. Finally, we describe the autonomous observing system and the dynamic scheduler that has increased the observing efficiency by a factor of 2-3 in comparison with static scheduling.
- MNRASErratum: FRB microstructure revealed by the real-time detection of FRB170827Farah, W., Flynn, C., Bailes, M., Jameson, A., Bannister, K. W., Barr, E. D., Bateman, T., Bhandari, S., Caleb, M., Campbell-Wilson, D., Chang, S. -W., Deller, A., Green, A. J., Hunstead, R., Jankowski, F., Keane, E., Macquart, J. -P., Möller, A., Onken, C. A., Osłowski, S., Parthasarathy, A., Plant, K., Ravi, V., Shannon, R. M., Tucker, B. E., Krishnan, V. Venkatraman, and Wolf, C.Mar 2019
- ATELDetection of FRB190322 at the Molonglo Radio TelescopeGupta, V., Bailes, M., Jameson, A., Flynn, C., Farah, W., Bateman, T., Barr, E. D., Bhandari, S., Caleb, M., Campbell-Wilson, D., Day, C., Deller, A., Green, A. J., Hunstead, R. W., Jankowski, F., Keane, E. F., Lower, M. E., Oslowski, S., Parthasarathy, A., Plant, K., Price, D. C., Ravi, V., Shannon, R. M., Sutherland, A., Temby, D., Torr, G., Urquhart, G., and Krishnan, V. VenkatramanMar 2019
At UTC 2019-03-22-07:00:12.3 (2019-03-22.29180903), we found a fast radio burst as part of the ongoing search program (UTMOST), at the Molonglo telescope. Molonglo is a 1.6 km long East-West array (Bailes et al 2017, PASA, 34, 45) and was operating in drift-scan mode with pointing centred on the meridian at the time of detection.
2018
- ATELDetection of FRB181228 at the Molonglo Radio TelescopeFarah, W., Bailes, M., Jameson, A., Flynn, C., Gupta, V., Bateman, T., Barr, E. D., Bhandari, S., Caleb, M., Campbell-Wilson, D., Day, C., Deller, A., Green, A. J., Hunstead, R. W., Jankowski, F., Keane, E. F., Lower, M. E., Oslowski, S., Parthasarathy, A., Plant, K., Price, D. C., Ravi, V., Shannon, R. M., Sutherland, A., Temby, D., Torr, G., Urquhart, G., and Krishnan, V. VenkatramanDec 2018
At UTC 2018-12-28-13:48:50.1 (2018-12-28.5755799), we found a bright fast radio burst as part of the ongoing search program (UTMOST), at the Molonglo telescope.
- ATELDetection of low-frequency radio emission from the magnetar XTE J1810-197Lower, M. E., Bailes, M., Jameson, A., Farah, W., Flynn, C., Gupta, V., Bateman, T., Barr, E. D., Bhandari, S., Caleb, M., Campbell-Wilson, D., Day, C., Deller, A., Green, A. J., Hunstead, R. W., Jankowski, F., Keane, E. F., Oslowski, S., Parthasarathy, A., Plant, K., Price, D. C., Ravi, V., Shannon, R. M., Sutherland, A., Temby, D., Torr, G., Urquhart, G., Krishnan, V. Venkatraman, and Venville, T.Dec 2018
Following the reported radio revival of the magnetar XTE J1810-197 (ATel #12284) and subsequent detection at high-frequencies (ATel #12285), we conducted low-frequency observations of the pulsar with the 1.6km Molonglo Observatory Synthesis Telescope as part of the UTMOST project (Bailes et al. 2017).
- PhyRevDParkes Pulsar Timing Array constraints on ultralight scalar-field dark matterPorayko, Nataliya K., Zhu, Xingjiang, Levin, Yuri, Hui, Lam, Hobbs, George, Grudskaya, Aleksandra, Postnov, Konstantin, Bailes, Matthew, Bhat, N. D. Ramesh, Coles, William, Dai, Shi, Dempsey, James, Keith, Michael J., Kerr, Matthew, Kramer, Michael, Lasky, Paul D., Manchester, Richard N., Osłowski, Stefan, Parthasarathy, Aditya, Ravi, Vikram, Reardon, Daniel J., Rosado, Pablo A., Russell, Christopher J., Shannon, Ryan M., Spiewak, Renée, van Straten, Willem, Toomey, Lawrence, Wang, Jingbo, Wen, Linqing, You, Xiaopeng, and PPTA Collaboration,Nov 2018
It is widely accepted that dark matter contributes about a quarter of the critical mass-energy density in our Universe. The nature of dark matter is currently unknown, with the mass of possible constituents spanning nearly one hundred orders of magnitude. The ultralight scalar field dark matter, consisting of extremely light bosons with m \ensuremath∼10^-22 eV and often called “fuzzy” dark matter, provides intriguing solutions to some challenges at sub-Galactic scales for the standard cold dark matter model. As shown by Khmelnitsky and Rubakov, such a scalar field in the Galaxy would produce an oscillating gravitational potential with nanohertz frequencies, resulting in periodic variations in the times of arrival of radio pulses from pulsars. The Parkes Pulsar Timing Array (PPTA) has been monitoring 20 millisecond pulsars at two- to three-week intervals for more than a decade. In addition to the detection of nanohertz gravitational waves, PPTA offers the opportunity for direct searches for fuzzy dark matter in an astrophysically feasible range of masses. We analyze the latest PPTA data set which includes timing observations for 26 pulsars made between 2004 and 2016. We perform a search in this data set for evidence of ultralight dark matter in the Galaxy using Bayesian and Frequentist methods. No statistically significant detection has been made. We, therefore, place upper limits on the local dark matter density. Our limits, improving on previous searches by a factor of 2 to 5, constrain the dark matter density of ultralight bosons with m \ensuremath≤10^-23 eV to be below 6 GeV cm^-3 with 95% confidence in the Earth neighborhood. Finally, we discuss the prospect of probing the astrophysically favored mass range m \ensuremath≳10^-22 eV with next-generation pulsar timing facilities.
- ATELTwo new FRBs discovered by UTMOSTFarah, W., Bailes, M., Jameson, A., Flynn, C., Gupta, V., Bateman, T., Barr, E. D., Bhandari, S., Caleb, M., Campbell-Wilson, D., Day, C., Deller, A., Green, A. J., Hunstead, R. W., Jankowski, F., Keane, E. F., Lower, M. E., Oslowski, S., Parthasarathy, A., Plant, K., Price, D. C., Ravi, V., Shannon, R. M., Sutherland, A., Temby, D., Torr, G., Urquhart, G., and Krishnan, V. VenkatramanOct 2018
At UTC 2018-10-16-04:16:56.3 (2018-10-16.1795823), we found a bright fast radio burst as part of the ongoing search program (UTMOST), at the Molonglo telescope.
- Notes of AASDetection of a Glitch in the Pulsar J1709-4429Lower, Marcus E., Flynn, Chris, Bailes, Matthew, Barr, Ewan D., Bateman, Timothy, Bhandari, Shivani, Caleb, Manisha, Campbell-Wilson, Duncan, Day, Cherie, Deller, Adam, Farah, Wael, Green, Anne J., Gupta, Vivek, Hunstead, Richard W., Jameson, Andrew, Jankowski, Fabian, Keane, Evan F., Venkatraman Krishnan, Vivek, Osłowski, Stefan, Parthasarathy, Aditya, Plant, Kathryn, Price, Danny C., Ravi, Vikram, Shannon, Ryan M., Temby, David, Torr, Glen, and Urquhart, GlennAug 2018
We report the detection of a glitch event in the pulsar J1709-4429 (also known as B1706-44) during regular monitoring observations with the Molonglo Observatory Synthesis Telescope (UTMOST). The glitch was found during timing operations, in which we regularly observe over 400 pulsars with up to daily cadence, while commensally searching for Rotating Radio Transients, pulsars, and FRBs. With a fractional size of PLACEHOLDERDeltaPLACEHOLDERnu/ν≈52.4 \times10^-9, the glitch reported here is by far the smallest known for this pulsar, attesting to the efficacy of glitch searches with high cadence using UTMOST.
- First interferometric detections of Fast Radio BurstsCaleb, M., Flynn, C., Bailes, M., Barr, E. D., Bateman, T., Bhandari, S., Campbell-Wilson, D., Farah, W., Green, A. J., Hunstead, R. W., Jameson, A., Jankowski, F., Keane, E. F., Parthasarathy, A., Ravi, V., Rosado, P. A., van Straten, W., and Krishnan, V. VenkatramanAug 2018
The class of radio transients called Fast Radio Bursts (FRBs) encompasses enigmatic single pulses, each unique in its own way, hindering a consensus for their origin. The key to demystifying FRBs lies in discovering many of them in order to identity commonalities - and in real time, in order to find potential counterparts at other wavelengths. The recently upgraded UTMOST in Australia, is undergoing a backend transformation to rise as a fast transient detection machine. The first interferometric detections of FRBs with UTMOST, place their origin beyond the near-field region of the telescope thus ruling out local sources of interference as a possible origin. We have localised these bursts to much better than the ones discovered at the Parkes radio telescope and have plans to upgrade UTMOST to be capable of much better localisation still.
- MNRASFRB microstructure revealed by the real-time detection of FRB170827Farah, W., Flynn, C., Bailes, M., Jameson, A., Bannister, K. W., Barr, E. D., Bateman, T., Bhandari, S., Caleb, M., Campbell-Wilson, D., Chang, S. -W., Deller, A., Green, A. J., Hunstead, R., Jankowski, F., Keane, E., Macquart, J. -P., Möller, A., Onken, C. A., Osłowski, S., Parthasarathy, A., Plant, K., Ravi, V., Shannon, R. M., Tucker, B. E., Venkatraman Krishnan, V., and Wolf, C.Jul 2018
We report a new fast radio burst (FRB) discovered in real-time as part of the UTMOST project at the Molonglo Observatory Synthesis Radio Telescope. FRB170827 was first detected with our low- latency (<24 s) and machine-learning based FRB detection system. The FRB discovery was accompanied by the capture of voltage data at the native time and frequency resolution of the observing system, enabling coherent dedispersion and detailed off-line analysis that have unveiled fine temporal and frequency structure. The dispersion measure (DM) of 176.80 \ensuremath\pm 0.04 pc cm^-3 is the lowest of the FRB population. The Milky Way contribution along the line of sight is \ensuremath∼40 pc cm^-3, leaving an excess DM of \ensuremath∼145 pc cm^-3. The FRB has a fluence >20 \ensuremath\pm 7 Jy ms, and is narrow with a width of \ensuremath∼400 {\ensuremathμ}s at 10 per cent of its maximum amplitude. However, the burst shows three temporal components, the narrowest of which is \ensuremath∼30 {\ensuremathμ}s, and a scattering time-scale of 4.1 \ensuremath\pm 2.7 {\ensuremathμ}s. The FRB shows spectral modulations on frequency scales of 1.5 MHz and 0.1 MHz. Both are prominent in the dynamic spectrum, which shows a very bright region of emission between 841 and 843 MHz, and weaker and patchy emission across the entire band. We show that the fine spectral structure could arise in the FRB host galaxy, or its immediate vicinity.
- ATELA fast radio burst towards the millisecond pulsar PSR J1744-1134 found during a commensal search by the Parkes Pulsar Timing ArrayOslowski, S., Shannon, R. M., Jameson, A., Russell, C. J., Bailes, M., Bhat, N. D. R., Coles, W. A., Dai, S., Dempsey, J., Hobbs, G., Keith, M. J., Kerr, M., Manchester, R. N., Lasky, P. D., Levin, Y., Parthasarathy, A., Ravi, V., Reardon, D. J., Sarkissian, J. M., Spiewak, R., van Straten, W., Toomey, L., Wang, J. B., Wen, L., You, X. P., Zhang, L., Zhang, S., and Zhu, X. J.Jul 2018
The Parkes Pulsar Timing Array (Manchester et al. 2013) project monitors pulse times of arrival for 24 millisecond pulsars in the Galaxy on a fortnightly cadence.
- ATELDetection of a Fast Radio Burst at the Molonglo Radio TelescopeFarah, W., Bailes, M., Jameson, A., Flynn, C., Gupta, V., Andreoni, I., Bateman, T., Barr, E. D., Bhandari, S., Caleb, M., Campbell-Wilson, D., Day, C., Deller, A., Green, A. J., Hunstead, R. W., Jankowski, F., Keane, E. F., Krishnan, V. Venkatraman, O’Neill, M., Oslowski, S., Parthasarathy, A., Plant, K., Price, D. C., Ravi, V., Shannon, R., Temby, D., Torr, G., and Urquhart, G.May 2018
On 2018-05-28-04:24:00.9 UTC (2018-05-28.18334375), UTMOST found a new FRB as part of the ongoing search program at the Molonglo Radio Telescope (see Bailes et al. 2017).
- ATELA second fast radio burst discovered with Parkes Telescope within 50 hours: FRB180311 in the direction of PSR J2129-5721Oslowski, S., Shannon, R. M., Jameson, Andrew, Hobbs, G., Bailes, M., Bhat, N. D. R., Coles, W. A., Dai, S., Dempsey, J., Keith, M. J., Kerr, M., Manchester, R. N., Lasky, D. P., Levin, Y., Parthasarathy, A., Ravi, V., Reardon, D. J., Russell, C. J., Sarkissian, J. M., Spiewak, R., Van Straten, W., Toomey, L., Wang, J. B., Wen, L., You, X. -P., Zhang, L., Zhang, S., and Zhu, X. -J.Mar 2018
The Parkes Pulsar Timing Array (Manchester et al. 2013) project monitors pulse times of arrival for 24 millisecond pulsars in the Galaxy on a fortnightly cadence using the multibeam receiver on the CSIRO 64-m Parkes Telescope.
- ATELReal-time detection of an extremely high signal-to-noise ratio fast radio burst during observations of PSR J2124-3358Oslowski, S., Shannon, R. M. ., Jameson, Andrew, Sarkissian, J. M. ., Bailes, M., Andreoni, I., Bhat, N. D. R. ., Coles, W. A., Dai, S., Dempsey, J., Hobbs, G., Keith, M. J., Kerr, M., Manchester, R. N., Lasky, P. D., Levin, Y., Parthasarathy, A., Ravi, V., Reardon, D. J., Rosado, P. A., Russell, C. J., Spiewak, R., Van Straten, W., Toomey, L., Wang, J. B., Wen, L., You, X. -P., Zhang, L., Zhang, S., and Zhu, X. -J.Mar 2018
The Parkes Pulsar Timing Array (Manchester et al. 2013) project monitors pulse times of arrival for 24 millisecond pulsars in the Galaxy on a fortnightly cadence using the multibeam receiver on the CSIRO 64-m Parkes Telescope.
2017
- ATELReal-time detection of a low-latitude Fast Radio Burst during observations of PSR J1545-4550Shannon, R. M., Oslowski, S., Zhang, S., Bailes, M., Bhat, R. N. D., Coles, W. A., Dai, S., Dempsey, J., Hobbs, G., Keith, M. J., Kerr, M., Jameson, A., Manchester, R. N., Lasky, P. D., Levin, Y., Parthasarathy, A., Ravi, V., Reardon, D. J., Rosado, P. A., Russell, C. J., Sarkissian, J. M., Spiewak, R., van Straten, W., Toomey, L., Wang, J. B., Wen, L., You, X. -P., Zhang, L., and Zhu, X. -J.Dec 2017
The Parkes Pulsar Timing Array (Manchester et al. 2013) project monitors pulse times of arrival for 24 millisecond pulsars in the Galaxy on a fortnightly cadence.
- PASAThe UTMOST: A Hybrid Digital Signal Processor Transforms the Molonglo Observatory Synthesis TelescopeBailes, M., Jameson, A., Flynn, C., Bateman, T., Barr, E. D., Bhandari, S., Bunton, J. D., Caleb, M., Campbell-Wilson, D., Farah, W., Gaensler, B., Green, A. J., Hunstead, R. W., Jankowski, F., Keane, E. F., Krishnan, V. Venkatraman, Murphy, Tara, O’Neill, M., Osłowski, S., Parthasarathy, A., Ravi, V., Rosado, P., and Temby, D.Oct 2017
The Molonglo Observatory Synthesis Telescope (MOST) is an 18000 m^2 radio telescope located 40 km from Canberra, Australia. Its operating band (820-851 MHz) is partly allocated to telecommunications, making radio astronomy challenging. We describe how the deployment of new digital receivers, Field Programmable Gate Array-based filterbanks, and server-class computers equipped with 43 Graphics Processing Units, has transformed the telescope into a versatile new instrument (UTMOST) for studying the radio sky on millisecond timescales. UTMOST has 10 times the bandwidth and double the field of view compared to the MOST, and voltage record and playback capability has facilitated rapid implementaton of many new observing modes, most of which operate commensally. UTMOST can simultaneously excise interference, make maps, coherently dedisperse pulsars, and perform real-time searches of coherent fan-beams for dispersed single pulses. UTMOST operates as a robotic facility, deciding how to efficiently target pulsars and how long to stay on source via real-time pulsar folding, while searching for single pulse events. Regular timing of over 300 pulsars has yielded seven pulsar glitches and three Fast Radio Bursts during commissioning. UTMOST demonstrates that if sufficient signal processing is applied to voltage streams, innovative science remains possible even in hostile radio frequency environments.
- ATELDetection of a highly scattered Fast Radio Burst at the Molonglo Radio TelescopeFarah, W., Bailes, M., Jameson, A., Flynn, C., Andreoni, I., Bateman, T., Barr, E. D., Bhandari, S., Caleb, M., Campbell-Wilson, D., Deller, A., Green, A. J., Hunstead, R. W., Jankowski, F., Keane, E. F., Krishnan, V. Venkatraman, O’Neill, M., Oslowski, S., Parthasarathy, A., Plant, K., Ravi, V., and Temby, D.Oct 2017
On 2017-09-22-11:23:33.4 UTC (2017-09-22.4746921296), UTMOST found a new FRB as part of the ongoing search program at the Molonglo Radio Telescope (see Bailes et al. 2017).
- ATELLarge glitch event observed in PSR J1731-4744Jankowski, Fabian, Bailes, Matthew, Barr, Ewan D., Bateman, Timothy, Bhandari, Shivani, Caleb, Manisha, Deller, Adam, Campbell-Wilson, Duncan, Farah, Wael, Flynn, Chris, Green, Anne J., Hunstead, Richard W., Jameson, Andrew, Keane, Evan F., Krishnan, Vivek Venkatraman, Plant, Kathryn, O’Neill, Morgan, Oslowski, Stefan, Parthasarathy, Aditya, Ravi, Vikram, and Temby, DaveSep 2017
We detected a large glitch event in the timing data of the pulsar J1731-4744, which we monitor routinely as part of the pulsar timing programme at the Molonglo Observatory Synthesis Radio Telescope (UTMOST project).
- ATELReal-time detection of a Fast Radio Burst at the Molonglo Radio TelescopeFarah, W., Flynn, C., Jameson, A., Bailes, M., Andreoni, I., Bateman, T., Barr, E. D., Bhandari, S., Caleb, M., Campbell-Wilson, D., Deller, A., Green, A. J., Hunstead, R. W., Jankowski, F., Keane, E. F., Krishnan, V. Venkatraman, Plant, K., O’Neill, M., Oslowski, S., Parthasarathy, A., Ravi, V., and Temby, D.Sep 2017
On 2017-08-27-16:20:18 UTC (2017-08-27.68076389), we found a bright burst as part of the ongoing FRB search program (UTMOST), at the Molonglo telescope. Molonglo is a 1.6 km long East-West array (see Bailes et al 2017, arxiv 1708.09619) and was operating in drift-scan mode with pointing centred on the meridian at the time of detection.
- MNRASThe first interferometric detections of fast radio burstsCaleb, M., Flynn, C., Bailes, M., Barr, E. D., Bateman, T., Bhandari, S., Campbell-Wilson, D., Farah, W., Green, A. J., Hunstead, R. W., Jameson, A., Jankowski, F., Keane, E. F., Parthasarathy, A., Ravi, V., Rosado, P. A., van Straten, W., and Venkatraman Krishnan, V.Jul 2017
We present the first interferometric detections of fast radio bursts (FRBs), an enigmatic new class of astrophysical transient. In a 180-d survey of the Southern sky, we discovered three FRBs at 843 MHz with the UTMOST array, as a part of commissioning science during a major ongoing upgrade. The wide field of view of UTMOST (\ensuremath≈9 deg^2) is well suited to FRB searches. The primary beam is covered by 352 partially overlapping fan-beams, each of which is searched for FRBs in real time with pulse widths in the range 0.655-42 ms, and dispersion measures \ensuremath≤2000 pc cm^-3. Detections of FRBs with the UTMOST array place a lower limit on their distances of \ensuremath≈10^4 km (limit of the telescope near-field) supporting the case for an astronomical origin. Repeating FRBs at UTMOST or an FRB detected simultaneously with the Parkes radio telescope and UTMOST would allow a few arcsec localization, thereby providing an excellent means of identifying FRB host galaxies, if present. Up to 100 h of followup for each FRB has been carried out with the UTMOST, with no repeating bursts seen. From the detected position, we present 3\ensuremathσ error ellipses of 15 arcsec \texttimes 8.4\textdegree on the sky for the point of origin for the FRBs. We estimate an all-sky FRB rate at 843 MHz above a fluence F_lim of 11 Jy ms of \ensuremath∼78 events sky^-1 d^-1 at the 95 per cent confidence level. The measured rate of FRBs at 843 MHz is two times higher than we had expected, scaling from the FRB rate at the Parkes radio telescope, assuming that FRBs have a flat spectral index and a uniform distribution in Euclidean space. We examine how this can be explained by FRBs having a steeper spectral index and/or a flatter logN-logF distribution than expected for a Euclidean Universe.
2016
- ATELGlitch event observed in the pulsar PSR J1740-3015Jankowski, Fabian, Bailes, Matthew, Barr, Ewan, Bateman, Timothy, Bhandari, Shivani, Caleb, Manisha, Campbell-Wilson, Duncan, Farah, Wael, Flynn, Chris, Green, Anne, Hunstead, Richard, Jameson, Andrew, Keane, Evan, Krishnan, Vivek Venkatraman, Parthasarathy, Aditya, and van Straten, WillemMay 2016
As part of the UTMOST project at the recently refurbished Molonglo Observatory Synthesis radio Telescope (MOST) near Canberra, Australia, we carry out a pulsar timing programme in which we observe a large number of pulsars with up to daily cadence.