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Peering into the Dark Side: Magnesium Lines Establish a Massive Neutron Star in PSR J2215+5135

Linares, M. ; Shahbaz, T. ; Casares, J.

The Astrophysical journal, 2018-05, Vol.859 (1), p.54 [Periódico revisado por pares]

Philadelphia: The American Astronomical Society

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Título:
Peering into the Dark Side: Magnesium Lines Establish a Massive Neutron Star in PSR J2215+5135
Autor: Linares, M. ; Shahbaz, T. ; Casares, J.
Assuntos: Astronomia i astrofísica ; Atmospheric absorption ; Balmer lines ; Binaries: general ; Center of gravity ; Companion stars ; Equations of state ; Fluxes ; Física ; Hydrogen ; Inclination ; Irradiation ; Light curve ; Magnesium ; Millisecond pulsars ; Neutron stars ; Neutrons ; Photometric observations ; Pulsars ; Pulsars: general ; pulsars: individual (PSR J2215+5135) ; Radial velocity ; Stars: neutron ; Stars: variables: general ; Velocity curve ; X-rays: binaries ; Àrees temàtiques de la UPC
É parte de: The Astrophysical journal, 2018-05, Vol.859 (1), p.54
Notas: High-Energy Phenomena and Fundamental Physics
AAS09051
Descrição: New millisecond pulsars (MSPs) in compact binaries provide a good opportunity to search for the most massive neutron stars. Their main-sequence companion stars are often strongly irradiated by the pulsar, displacing the effective center of light from their barycenter and making mass measurements uncertain. We present a series of optical spectroscopic and photometric observations of PSR J2215+5135, a "redback" binary MSP in a 4.14 hr orbit, and measure a drastic temperature contrast between the dark/cold (TN = 5660 K) and bright/hot (TD = 8080 K) sides of the companion star. We find that the radial velocities depend systematically on the atmospheric absorption lines used to measure them. Namely, the semi-amplitude of the radial velocity curve (RVC) of J2215 measured with magnesium triplet lines is systematically higher than that measured with hydrogen Balmer lines, by 10%. We interpret this as a consequence of strong irradiation, whereby metallic lines dominate the dark side of the companion (which moves faster) and Balmer lines trace its bright (slower) side. Further, using a physical model of an irradiated star to fit simultaneously the two-species RVCs and the three-band light curves, we find a center-of-mass velocity of K2 = 412.3 5.0 km s−1 and an orbital inclination i = 63 9 . Our model is able to reproduce the observed fluxes and velocities without invoking irradiation by an extended source. We measure masses of M1 = 2.27 M and M2 = 0.33 M for the neutron star and the companion star, respectively. If confirmed, such a massive pulsar would rule out some of the proposed equations of state for the neutron star interior.
Editor: Philadelphia: The American Astronomical Society
Idioma: Inglês

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Peering into the Dark Side: Magnesium Lines Establish a Massive Neutron Star in PSR J2215+5135

Linares, M. ; Shahbaz, T. ; Casares, J.

Philadelphia: The American Astronomical Society

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