Masses of optical components and black holes in x-ray novae: the effects of components proximity

Abstract

An exact calculation of CaI $\lambda 6439.075$A absorption profiles in the spectra of optical stars in low-mass X-ray binary systems with black holes (BH LMXBs) is carried out. We show that the approximation of a real Roche lobe filling star as disk with uniform local line profile and linear limb darkening law leads to overestimation of projected equatorial rotational velocity $V_{rot}\sin i$ and accordingly, underestimation of mass ratio $q=M_x/M_v$. Refined value of $q$ does not affect the mass of a black hole, but the mass of an optical star has shrunk $\sim 1.5$ times. We present refined components masses in low-mass X-ray binaries with black holes. Companion masses in BH LMXBs are found in the mass range 0.1 - 1.6 $M_{\odot }$ with the peak at $M_v\simeq 0.35M_{\odot }$. This finding poses additional problem for the standard evolutionary scenarios of BH LMXBs formation with a common envelope phase (CE). We also discuss the implications of these masses into the evolutionary history of the binary.

12 pages, 2 figures, 2 tables

References in corpus (3)

• The Origin of Black Hole Spin in Galactic Low-Mass X-ray Binaries
• Chemical Abundances of the Secondary Star in the Black Hole X-ray Binary XTE J1118+480
• The rotational broadening of V395 Car - implications on compact object's mass

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• Population synthesis of AX J1745.6-2901 X-ray nova type binaries with rapidly decreasing orbital periods