Bibcode
Casares, J.
Referencia bibliográfica
The Astrophysical Journal, Volume 808, Issue 1, article id. 80, 11 pp. (2015).
Fecha de publicación:
7
2015
Revista
Número de citas
59
Número de citas referidas
56
Descripción
We compare {{{H}}}α emission profiles of 12
dynamically confirmed black holes (BHs) and 2 neutron star X-ray
transients (SXTs) in quiescence with those of a sample of 43 Cataclysmic
Variables (CVs), also quiescent. The FWHM of the {{{H}}}α
line in SXTs is tightly correlated with the velocity
semi-amplitude of the donor star {K}2=0.233(13){FWHM}. This
new correlation, when combined with orbital periods (i.e., through
photometric light curves), allows for the possibility of estimating
compact object mass functions from single integration, low-resolution
spectroscopy. On the other hand, CVs above the period gap are found to
follow a flatter correlation, a likely consequence of their larger mass
ratios. We also find that the FWHM traces the disk velocity at ≈ 42%
{R}L1, independently of binary mass ratio. In addition, for a
given FWHM, BHs tend to have lower EWs than CVs. This might be explained
by the fact that CVs must be seen at higher inclinations to mimic the
same projected disk velocities as BH SXTs. For the same reason, CVs with
{FWHM}≳ 1500 km s‑1 are mostly eclipsing while
none of our sample BHs are. Furthermore, we show that there is a
vacant/unoccupied region for CVs in the FWHM–EW plane defined by
{FWHM}\gt 2568\sqrt{(1-{(9/{EW})}2)} ({km}
{{{s}}}-1). Both the FWHM–K2 correlation and
the FWHM–EW plane can be exploited, together with photometric
light curves, to efficiently discover quiescent BHs in deep
{{{H}}}α surveys of the Galactic plane.
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