M. K. Abubekerov, E. A. Antokhina, A. M. Cherepashchuk, V. V. Shimanskii
We interpret the observed radial-velocity curve of the optical star in the
low-mass X-ray binary 2S 0921-630 using a Roche model, taking into account the
X-ray heating of the optical star and screening of X-rays coming from the
relativistic object by the accretion disk. Consequences of possible anisotropy
of the X-ray radiation are considered.We obtain relations between the masses of
the optical and compact (X-ray) components, mv and mx, for orbital inclinations
i=60, 75, 90 degrees. Including X-ray heating enabled us to reduce the compact
object's mass by near 0.5-1Msun, compared to the case with no heating. Based on
the K0III spectral type of the optical component (with a probable mass of
mv=2.9Msun, we concluded that mx=2.45-2.55Msun (for i=75-90 degrees). If the
K0III star has lost a substantial part of its mass as a result of mass
exchange, as in the V404 Cyg and GRS 1905+105 systems, and its mass is
$m_v=0.65-0.75Msun, the compact object's mass is close to the standard mass of
a neutron star, mx=1.4Msun (for i=75-90 degrees). Thus, it is probable that the
X-ray source in the 2S 0921-630 binary is an accreting neutron star.
View original:
http://arxiv.org/abs/1201.4689
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