The Black Hole Binary V4641 Sagitarii: Activity in Quiescence & Improved Mass Determinations

摘要: We examine ~10 years of photometric data and find that the black hole X-ray binary V4641 Sgr has two optical states, passive active, during quiescence. The state is dominated by ellipsoidal variations stable in shape variability light curve. active brighter more variable. Emission varies over course orbital period redder than companion star. These optical/infrared states last for weeks or months. spends approximately 85% quiescence 15% active. analyze colors spectroscopy show they are consistent with a reddened B9III star (with E(B-V) = 0.37 +/- 0.19) little no contribution from accretion disk. use observations an updated ephemeris to place upper limit on duration eclipse <8.3 deg phase (~1.6 hours). High resolution yields greatly improved measurement rotational velocity V_rot_sin(i) 100.9 0.8 km s^-1. fit models inclination angle i 72.3 4.1 deg, mass ratio Q 2.2 0.2, component masses system M_BH 6.4 0.6 M_sun M_2 2.9 0.4 M_sun. Using these values we calculate distance 6.2 0.7 kpc.