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8 results on '"Rammala, I."'

1. The MPIfR-MeerKAT Galactic Plane Survey II. The eccentric double neutron star system PSR J1208-5936 and a neutron star merger rate update

Author

Bernadich, M. Colom i, Balakrishnan, V., Barr, E., Berezina, M., Burgay, M., Buchner, S., Champion, D. J., Chen, W., Desvignes, G., Freire, P. C. C., Grunthal, K., Kramer, M., Men, Y., Padmanabh, P. V., Parthasarathy, A., Pillay, D., Rammala, I., Sengupta, S., and Krishnan, V. Venkatraman

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The MMGPS-L is the most sensitive pulsar survey in the Southern Hemisphere. We present a follow-up study of one of these new discoveries, PSR J1208-5936, a 28.71-ms recycled pulsar in a double neutron star system with an orbital period of Pb=0.632 days and an eccentricity of e=0.348. Through timing of almost one year of observations, we detected the relativistic advance of periastron (0.918(1) deg/yr), resulting in a total system mass of Mt=2.586(5) Mo. We also achieved low-significance constraints on the amplitude of the Einstein delay and Shapiro delay, in turn yielding constraints on the pulsar mass (Mp=1.26(+0.13/-0.25) Mo), the companion mass (Mc=1.32(+0.25/-0.13) Mo, and the inclination angle (i=57(12) degrees). This system is highly eccentric compared to other Galactic field double neutron stars with similar periods, possibly hinting at a larger-than-usual supernova kick during the formation of the second-born neutron star. The binary will merge within 7.2(2) Gyr due to the emission of gravitational waves. With the improved sensitivity of the MMGPS-L, we updated the Milky Way neutron star merger rate to be 25(+19/-9) Myr$^{-1}$ within 90% credible intervals, which is lower than previous studies based on known Galactic binaries owing to the lack of further detections despite the highly sensitive nature of the survey. This implies a local cosmic neutron star merger rate of 293(+222/-103} Gpc/yr, consistent with LIGO and Virgo O3 observations. With this, we predict the observation of 10(+8/-4) neutron star merger events during the LIGO-Virgo-KAGRA O4 run. We predict the uncertainties on the component masses and the inclination angle will be reduced to 5x10$^{-3}$ Mo and 0.4 degrees after two decades of timing, and that in at least a decade from now the detection of the shift in Pb and the sky proper motion will serve to make an independent constraint of the distance to the system.

Published
2023
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2. The 1.28 GHz MeerKAT Galactic Center Mosaic

Author

Heywood, I., Rammala, I., Camilo, F., Cotton, W. D., Yusef-Zadeh, F., Abbott, T. D., Adam, R. M., Adams, G., Aldera, M. A., Asad, K. M. B., Bauermeister, E. F., Bennett, T. G. H., Bester, H. L., Bode, W. A., Botha, D. H., Botha, A. G., Brederode, L. R. S., Buchner, S., Burger, J. P., Cheetham, T., de Villiers, D. I. L., Dikgale-Mahlakoana, M. A., Toit, L. J. du, Esterhuyse, S. W. P., Fanaroff, B. L., February, S., Fourie, D. J., Frank, B. S., Gamatham, R. R. G., Geyer, M., Goedhart, S., Gouws, M., Gumede, S. C., Hlakola, M. J., Hokwana, A., Hoosen, S. W., Horrell, J. M. G., Hugo, B., Isaacson, A. I., Józsa, G. I. G., Jonas, J. L., Joubert, A. F., Julie, R. P. M., Kapp, F. B., Kenyon, J. S., Kotzé, P. P. A., Kriek, N., Kriel, H., Krishnan, V. K., Lehmensiek, R., Liebenberg, D., Lord, R. T., Lunsky, B. M., Madisa, K., Magnus, L. G., Mahgoub, O., Makhaba, A., Makhathini, S., Malan, J. A., Manley, J. R., Marais, S. J., Martens, A., Mauch, T., Merry, B. C., Millenaar, R. P., Mnyandu, N., Mokone, O. J., Monama, T. E., Mphego, M. C., New, W. S., Ngcebetsha, B., Ngoasheng, K. J., Ockards, M. T., Oozeer, N., Otto, A. J., Passmoor, S. S., Patel, A. A., Peens-Hough, A., Perkins, S. J., Ramaila, A. J. T., Ramanujam, N. M. R., Ramudzuli, Z. R., Ratcliffe, S. M., Robyntjies, A., Salie, S., Sambu, N., Schollar, C. T. G., Schwardt, L. C., Schwartz, R. L., Serylak, M., Siebrits, R., Sirothia, S. K., Slabber, M., Smirnov, O. M., Sofeya, L., Taljaard, B., Tasse, C., Tiplady, A. J., Toruvanda, O., Twum, S. N., van Balla, T. J., van der Byl, A., van der Merwe, C., Van Tonder, V., Van Wyk, R., Venter, A. J., Venter, M., Wallace, B. H., Welz, M. G., Williams, L. P., and Xaia, B.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

The inner $\sim$200 pc region of the Galaxy contains a 4 million M$_{\odot}$ supermassive black hole (SMBH), significant quantities of molecular gas, and star formation and cosmic ray energy densities that are roughly two orders of magnitude higher than the corresponding levels in the Galactic disk. At a distance of only 8.2 kpc, the region presents astronomers with a unique opportunity to study a diverse range of energetic astrophysical phenomena, from stellar objects in extreme environments, to the SMBH and star-formation driven feedback processes that are known to influence the evolution of galaxies as a whole. We present a new survey of the Galactic center conducted with the South African MeerKAT radio telescope. Radio imaging offers a view that is unaffected by the large quantities of dust that obscure the region at other wavelengths, and a scene of striking complexity is revealed. We produce total intensity and spectral index mosaics of the region from 20 pointings (144 hours on-target in total), covering 6.5 square degrees with an angular resolution of 4$"$,at a central frequency of 1.28 GHz. Many new features are revealed for the first time due to a combination of MeerKAT's high sensitivity, exceptional $u,v$-plane coverage, and geographical vantage point. We highlight some initial survey results, including new supernova remnant candidates, many new non-thermal filament complexes, and enhanced views of the Radio Arc Bubble, Sgr A and Sgr B regions. This project is a SARAO public legacy survey, and the image products are made available with this article., Comment: 29 pages, 15 figures, 3 tables, accepted for publication in the The Astrophysical Journal. Replacement arXiv version with higher quality figures

Published
2022
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3. Revival of the magnetar PSR J1622-4950: observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR

Author

Camilo, F., Scholz, P., Serylak, M., Buchner, S., Merryfield, M., Kaspi, V. M., Archibald, R. F., Bailes, M., Jameson, A., van Straten, W., Sarkissian, J., Reynolds, J. E., Johnston, S., Hobbs, G., Abbott, T. D., Adam, R. M., Adams, G. B., Alberts, T., Andreas, R., Asad, K. M. B., Baker, D. E., Baloyi, T., Bauermeister, E. F., Baxana, T., Bennett, T. G. H., Bernardi, G., Booisen, D., Booth, R. S., Botha, D. H., Boyana, L., Brederode, L. R. S., Burger, J. P., Cheetham, T., Conradie, J., Conradie, J. P., Davidson, D. B., de Bruin, G., de Swardt, B., de Villiers, C., de Villiers, D. I. L., de Villiers, M. S., de Villiers, W., de Waal, C., Dikgale, M. A., Toit, G. du, Toit, L. J. du, Esterhuyse, S. W. P., Fanaroff, B., Fataar, S., Foley, A. R., Foster, G., Fourie, D., Gamatham, R., Gatsi, T., Geschke, R., Goedhart, S., Grobler, T. L., Gumede, S. C., Hlakola, M. J., Hokwana, A., Hoorn, D. H., Horn, D., Horrell, J., Hugo, B., Isaacson, A., Jacobs, O., van Rensburg, J. P. Jansen, Jonas, J. L., Jordaan, B., Joubert, A., Joubert, F., Jozsa, G. I. G., Julie, R., Julius, C. C., Kapp, F., Karastergiou, A., Karels, F., Kariseb, M., Karuppusamy, R., Kasper, V., Knox-Davies, E. C., Koch, D., Kotze, P. P. A., Krebs, A., Kriek, N., Kriel, H., Kusel, T., Lamoor, S., Lehmensiek, R., Liebenberg, D., Liebenberg, I., Lord, R. T., Lunsky, B., Mabombo, N., Macdonald, T., Macfarlane, P., Madisa, K., Mafhungo, L., Magnus, L. G., Magozore, C., Mahgoub, O., Main, J. P. L., Makhathini, S., Malan, J. A., Malgas, P., Manley, J. R., Manzini, M., Marais, L., Marais, N., Marais, S. J., Maree, M., Martens, A., Matshawule, S. D., Matthysen, N., Mauch, T., Nally, L. D. Mc, Merry, B., Millenaar, R. P., Mjikelo, C., Mkhabela, N., Mnyandu, N., Moeng, I. T., Mokone, O. J., Monama, T. E., Montshiwa, K., Moss, V., Mphego, M., New, W., Ngcebetsha, B., Ngoasheng, K., Niehaus, H., Ntuli, P., Nzama, A., Obies, F., Obrocka, M., Ockards, M. T., Olyn, C., Oozeer, N., Otto, A. J., Padayachee, Y., Passmoor, S., Patel, A. A., Paula, S., Peens-Hough, A., Pholoholo, B., Prozesky, P., Rakoma, S., Ramaila, A. J. T., Rammala, I., Ramudzuli, Z. R., Rasivhaga, M., Ratcliffe, S., Reader, H. C., Renil, R., Richter, L., Robyntjies, A., Rosekrans, D., Rust, A., Salie, S., Sambu, N., Schollar, C. T. G., Schwardt, L., Seranyane, S., Sethosa, G., Sharpe, C., Siebrits, R., Sirothia, S. K., Slabber, M. J., Smirnov, O., Smith, S., Sofeya, L., Songqumase, N., Spann, R., Stappers, B., Steyn, D., Steyn, T. J., Strong, R., Struthers, A., Stuart, C., Sunnylall, P., Swart, P. S., Taljaard, B., Tasse, C., Taylor, G., Theron, I. P., Thondikulam, V., Thorat, K., Tiplady, A., Toruvanda, O., van Aardt, J., van Balla, T., Heever, L. van den, van der Byl, A., van der Merwe, C., van der Merwe, P., van Niekerk, P. C., van Rooyen, R., van Staden, J. P., van Tonder, V., van Wyk, R., Wait, I., Walker, A. L., Wallace, B., Welz, M., Williams, L. P., Xaia, B., Young, N., and Zitha, S.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, reactivated between 2017 March 19 and April 5. The radio flux density, while variable, is approximately 100x larger than during its dormant state. The X-ray flux one month after reactivation was at least 800x larger than during quiescence, and has been decaying exponentially on a 111+/-19 day timescale. This high-flux state, together with a radio-derived rotational ephemeris, enabled for the first time the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV pulsed fraction is comparable to the smallest observed for magnetars. The overall pulsar geometry inferred from polarized radio emission appears to be broadly consistent with that determined 6-8 years earlier. However, rotating vector model fits suggest that we are now seeing radio emission from a different location in the magnetosphere than previously. This indicates a novel way in which radio emission from magnetars can differ from that of ordinary pulsars. The torque on the neutron star is varying rapidly and unsteadily, as is common for magnetars following outburst, having changed by a factor of 7 within six months of reactivation., Comment: Published in ApJ (2018 April 5); 13 pages, 4 figures

Published
2018
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4. The MPIfR-MeerKAT Galactic Plane Survey

Author

Colom i Bernadich, M., primary, Balakrishnan, V., additional, Barr, E., additional, Berezina, M., additional, Burgay, M., additional, Buchner, S., additional, Champion, D. J., additional, Chen, W., additional, Desvignes, G., additional, Freire, P. C. C., additional, Grunthal, K., additional, Kramer, M., additional, Men, Y., additional, Padmanabh, P. V., additional, Parthasarathy, A., additional, Pillay, D., additional, Rammala, I., additional, Sengupta, S., additional, and Venkatraman Krishnan, V., additional

Published
2023
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5. The MPIfR-MeerKAT Galactic Plane Survey: II. The eccentric double neutron star system PSR J1208a-5936 and a neutron star merger rate update

Author

Colom i Bernadich, M., Balakrishnan, V., Barr, E., Berezina, M., Burgay, M., Buchner, S., Champion, D.J., Chen, W., Desvignes, G., Freire, P.C.C., Grunthal, K., Kramer, M., Men, Y., Padmanabh, P.V., Parthasarathy, A., Pillay, D., Rammala, I., Sengupta, S., Venkatraman, Krishnan V., Colom i Bernadich, M., Balakrishnan, V., Barr, E., Berezina, M., Burgay, M., Buchner, S., Champion, D.J., Chen, W., Desvignes, G., Freire, P.C.C., Grunthal, K., Kramer, M., Men, Y., Padmanabh, P.V., Parthasarathy, A., Pillay, D., Rammala, I., Sengupta, S., and Venkatraman, Krishnan V.

Abstract

The MPIfR-MeerKAT Galactic Plane survey at L-band (MMGPS-L) is the most sensitive pulsar survey in the Southern Hemisphere, providing 78 discoveries in an area of 900 sq. deg. Here, we present a follow-up study of one of these new discoveries, PSR J1208a-5936, a 28.71-ms recycled pulsar in a double neutron star system with an orbital period of Pb=0.632 days and an eccentricity of e=0.348, merging within the Hubble time. Through timing of almost one year of observations, we detected the relativistic advance of periastron ( Ì = 0.918(1) deg yra-1), resulting in a total system mass of Mt=2.586(5) M·. We also achieved low-significance constraints on the amplitude of the Einstein delay and Shapiro delay, in turn yielding constraints on the pulsar mass (Mp = 1.26a-0.25+0.13 M·), the companion mass (Mc = 1.32a-0.13+0.25 M·), and the inclination angle (i=57 ± 12). This system is highly eccentric compared to other Galactic field double neutron stars with similar periods, possibly hinting at a larger-than-usual supernova kick during the formation of the second-born neutron star. The binary will merge within 7.2(2) Gyr due to the emission of gravitational waves, making it a progenitor of the neutron star merger events seen by ground-based gravitational wave observatories. With the improved sensitivity of the MMGPS-L, we updated the Milky Way neutron star merger rate to be RMWnew = 25a-9+19 Myra-1 within 90% credible intervals, which is lower than previous studies based on known Galactic binaries owing to the lack of further detections despite the highly sensitive nature of the survey. This implies a local cosmic neutron star merger rate of Rlocalnew = 293a-103+222 Gpca-3 yra-1, which is consistent with LIGO and Virgo O3 observations. With this, we also predict the observation of 10a-4+8 neutron star merger events during the LIGO-Virgo-KAGRA O4 run. We predict the uncertainties on the component masses and the inclination angle will be reduced to 5- 10a-3 M· and 0.4 after two de

Published
2023

6. The 1.28 GHz MeerKAT Galactic Center Mosaic

Author

Heywood, I., primary, Rammala, I., additional, Camilo, F., additional, Cotton, W. D., additional, Yusef-Zadeh, F., additional, Abbott, T. D., additional, Adam, R. M., additional, Adams, G., additional, Aldera, M. A., additional, Asad, K. M. B., additional, Bauermeister, E. F., additional, Bennett, T. G. H., additional, Bester, H. L., additional, Bode, W. A., additional, Botha, D. H., additional, Botha, A. G., additional, Brederode, L. R. S., additional, Buchner, S., additional, Burger, J. P., additional, Cheetham, T., additional, de Villiers, D. I. L., additional, Dikgale-Mahlakoana, M. A., additional, du Toit, L. J., additional, Esterhuyse, S. W. P., additional, Fanaroff, B. L., additional, February, S., additional, Fourie, D. J., additional, Frank, B. S., additional, Gamatham, R. R. G., additional, Geyer, M., additional, Goedhart, S., additional, Gouws, M., additional, Gumede, S. C., additional, Hlakola, M. J., additional, Hokwana, A., additional, Hoosen, S. W., additional, Horrell, J. M. G., additional, Hugo, B., additional, Isaacson, A. I., additional, Józsa, G. I. G., additional, Jonas, J. L., additional, Joubert, A. F., additional, Julie, R. P. M., additional, Kapp, F. B., additional, Kenyon, J. S., additional, Kotzé, P. P. A., additional, Kriek, N., additional, Kriel, H., additional, Krishnan, V. K., additional, Lehmensiek, R., additional, Liebenberg, D., additional, Lord, R. T., additional, Lunsky, B. M., additional, Madisa, K., additional, Magnus, L. G., additional, Mahgoub, O., additional, Makhaba, A., additional, Makhathini, S., additional, Malan, J. A., additional, Manley, J. R., additional, Marais, S. J., additional, Martens, A., additional, Mauch, T., additional, Merry, B. C., additional, Millenaar, R. P., additional, Mnyandu, N., additional, Mokone, O. J., additional, Monama, T. E., additional, Mphego, M. C., additional, New, W. S., additional, Ngcebetsha, B., additional, Ngoasheng, K. J., additional, Ockards, M. T., additional, Oozeer, N., additional, Otto, A. J., additional, Passmoor, S. S., additional, Patel, A. A., additional, Peens-Hough, A., additional, Perkins, S. J., additional, Ramaila, A. J. T., additional, Ramanujam, N. M. R., additional, Ramudzuli, Z. R., additional, Ratcliffe, S. M., additional, Robyntjies, A., additional, Salie, S., additional, Sambu, N., additional, Schollar, C. T. G., additional, Schwardt, L. C., additional, Schwartz, R. L., additional, Serylak, M., additional, Siebrits, R., additional, Sirothia, S. K., additional, Slabber, M., additional, Smirnov, O. M., additional, Sofeya, L., additional, Taljaard, B., additional, Tasse, C., additional, Tiplady, A. J., additional, Toruvanda, O., additional, Twum, S. N., additional, van Balla, T. J., additional, van der Byl, A., additional, van der Merwe, C., additional, Van Tonder, V., additional, Van Wyk, R., additional, Venter, A. J., additional, Venter, M., additional, Wallace, B. H., additional, Welz, M. G., additional, Williams, L. P., additional, and Xaia, B., additional

Published
2022
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8. Revival of the Magnetar PSR J1622–4950: Observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR

Author

Camilo, F., primary, Scholz, P., additional, Serylak, M., additional, Buchner, S., additional, Merryfield, M., additional, Kaspi, V. M., additional, Archibald, R. F., additional, Bailes, M., additional, Jameson, A., additional, Straten, W. van, additional, Sarkissian, J., additional, Reynolds, J. E., additional, Johnston, S., additional, Hobbs, G., additional, Abbott, T. D., additional, Adam, R. M., additional, Adams, G. B., additional, Alberts, T., additional, Andreas, R., additional, Asad, K. M. B., additional, Baker, D. E., additional, Baloyi, T., additional, Bauermeister, E. F., additional, Baxana, T., additional, Bennett, T. G. H., additional, Bernardi, G., additional, Booisen, D., additional, Booth, R. S., additional, Botha, D. H., additional, Boyana, L., additional, Brederode, L. R. S., additional, Burger, J. P., additional, Cheetham, T., additional, Conradie, J., additional, Conradie, J. P., additional, Davidson, D. B., additional, Bruin, G. De, additional, Swardt, B. de, additional, Villiers, C. de, additional, Villiers, D. I. L. de, additional, Villiers, M. S. de, additional, Villiers, W. de, additional, Waal, C. De, additional, Dikgale, M. A., additional, Toit, G. du, additional, Toit, L. J. du, additional, Esterhuyse, S. W. P., additional, Fanaroff, B., additional, Fataar, S., additional, Foley, A. R., additional, Foster, G., additional, Fourie, D., additional, Gamatham, R., additional, Gatsi, T., additional, Geschke, R., additional, Goedhart, S., additional, Grobler, T. L., additional, Gumede, S. C., additional, Hlakola, M. J., additional, Hokwana, A., additional, Hoorn, D. H., additional, Horn, D., additional, Horrell, J., additional, Hugo, B., additional, Isaacson, A., additional, Jacobs, O., additional, van Rensburg, J. P. Jansen, additional, Jonas, J. L., additional, Jordaan, B., additional, Joubert, A., additional, Joubert, F., additional, Józsa, G. I. G., additional, Julie, R., additional, Julius, C. C., additional, Kapp, F., additional, Karastergiou, A., additional, Karels, F., additional, Kariseb, M., additional, Karuppusamy, R., additional, Kasper, V., additional, Knox-Davies, E. C., additional, Koch, D., additional, Kotzé, P. P. A., additional, Krebs, A., additional, Kriek, N., additional, Kriel, H., additional, Kusel, T., additional, Lamoor, S., additional, Lehmensiek, R., additional, Liebenberg, D., additional, Liebenberg, I., additional, Lord, R. T., additional, Lunsky, B., additional, Mabombo, N., additional, Macdonald, T., additional, Macfarlane, P., additional, Madisa, K., additional, Mafhungo, L., additional, Magnus, L. G., additional, Magozore, C., additional, Mahgoub, O., additional, Main, J. P. L., additional, Makhathini, S., additional, Malan, J. A., additional, Malgas, P., additional, Manley, J. R., additional, Manzini, M., additional, Marais, L., additional, Marais, N., additional, Marais, S. J., additional, Maree, M., additional, Martens, A., additional, Matshawule, S. D., additional, Matthysen, N., additional, Mauch, T., additional, Nally, L. D. Mc, additional, Merry, B., additional, Millenaar, R. P., additional, Mjikelo, C., additional, Mkhabela, N., additional, Mnyandu, N., additional, Moeng, I. T., additional, Mokone, O. J., additional, Monama, T. E., additional, Montshiwa, K., additional, Moss, V., additional, Mphego, M., additional, New, W., additional, Ngcebetsha, B., additional, Ngoasheng, K., additional, Niehaus, H., additional, Ntuli, P., additional, Nzama, A., additional, Obies, F., additional, Obrocka, M., additional, Ockards, M. T., additional, Olyn, C., additional, Oozeer, N., additional, Otto, A. J., additional, Padayachee, Y., additional, Passmoor, S., additional, Patel, A. A., additional, Paula, S., additional, Peens-Hough, A., additional, Pholoholo, B., additional, Prozesky, P., additional, Rakoma, S., additional, Ramaila, A. J. T., additional, Rammala, I., additional, Ramudzuli, Z. R., additional, Rasivhaga, M., additional, Ratcliffe, S., additional, Reader, H. C., additional, Renil, R., additional, Richter, L., additional, Robyntjies, A., additional, Rosekrans, D., additional, Rust, A., additional, Salie, S., additional, Sambu, N., additional, Schollar, C. T. G., additional, Schwardt, L., additional, Seranyane, S., additional, Sethosa, G., additional, Sharpe, C., additional, Siebrits, R., additional, Sirothia, S. K., additional, Slabber, M. J., additional, Smirnov, O., additional, Smith, S., additional, Sofeya, L., additional, Songqumase, N., additional, Spann, R., additional, Stappers, B., additional, Steyn, D., additional, Steyn, T. J., additional, Strong, R., additional, Struthers, A., additional, Stuart, C., additional, Sunnylall, P., additional, Swart, P. S., additional, Taljaard, B., additional, Tasse, C., additional, Taylor, G., additional, Theron, I. P., additional, Thondikulam, V., additional, Thorat, K., additional, Tiplady, A., additional, Toruvanda, O., additional, Aardt, J. van, additional, Balla, T. van, additional, Heever, L. van den, additional, Byl, A. van der, additional, Merwe, C. van der, additional, Merwe, P. van der, additional, Niekerk, P. C. van, additional, Rooyen, R. van, additional, Staden, J. P. van, additional, Tonder, V. van, additional, Wyk, R. van, additional, Wait, I., additional, Walker, A. L., additional, Wallace, B., additional, Welz, M., additional, Williams, L. P., additional, Xaia, B., additional, Young, N., additional, and Zitha, S., additional

Published
2018
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