Measuring the mass of the black widow PSR J1555-2908

Journal Article · Fri Feb 18 00:00:00 EST 2022 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stac379· OSTI ID:1860445

Kennedy, M. R. ^[1]; Breton, R. P. ^[2]; Clark, C. J. ^[3]; Mata Sánchez, D. ^[4]; Voisin, G. ^[5]; Dhillon, V. S. ^[6]; Halpern, J. P. ^[7]; Marsh, T. R. ^[8]; Nieder, L. ^[9]; Ray, P. S. ^[10]; van Kerkwijk, M. H. ^[11]

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1. Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, M19 9PL, UK, Department of Physics, University College Cork, Cork, Ireland
2. Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, M19 9PL, UK
3. Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, M19 9PL, UK, Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Callinstraße 38, D-30167 Hannover, Germany, Leibniz Universität Hannover, D-30167 Hannover, Germany
4. Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, M19 9PL, UK, Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain, Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
5. LUTH, Observatoire de Paris, PSL Research University, CNRS, 5 Place Jules Janssen, F-92190 Meudon, France, Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, M19 9PL, UK
6. Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain, Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
7. Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027, USA
8. Department of Physics, University of Warwick, Coventry CV4 7AL, UK
9. Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Callinstraße 38, D-30167 Hannover, Germany, Leibniz Universität Hannover, D-30167 Hannover, Germany
10. Space Science Division, U.S. Naval Research Laboratory, Washington, DC 20375, USA
11. Department of Astronomy and Astrophysics, University of Toronto, 50 George Street, Toronto, Ontario, M5S 3H4, Canada

ABSTRACT

Accurate measurements of the masses of neutron stars are necessary to test binary evolution models, and to constrain the neutron star equation of state. In pulsar binaries with no measurable post-Keplerian parameters, this requires an accurate estimate of the binary system’s inclination and the radial velocity of the companion star by other means than pulsar timing. In this paper, we present the results of a new method for measuring this radial velocity using the binary synthesis code Icarus. This method relies on constructing a model spectrum of a tidally distorted, irradiated star as viewed for a given binary configuration. This method is applied to optical spectra of the newly discovered black widow PSR J1555–2908. By modeling the optical spectroscopy alongside optical photometry, we find that the radial velocity of the companion star is 397 ± 4 km s−1 (errors quoted at 95 per cent confidence interval), as well as a binary inclination of >75°. Combined with γ-ray pulsation timing information, this gives a neutron star mass of 1.67$$^{+0.15}_{-0.09}$$ M⊙ and a companion mass of 0.060$$^{+0.005}_{-0.003}$$ M⊙, placing PSR J1555–2908 at the observed upper limit of what is considered a black widow system.

• Sponsoring Organization: USDOE
• OSTI ID: 1860445
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 2 Vol. 512; ISSN 0035-8711
• Publisher: Oxford University Press
• Country of Publication: United Kingdom
• Language: English