Evidence for Another Black Hole Binary: X-ray Nova Ophiuci 1977
Session 102 -- X-Ray Variables, Binaries and Transients
Display presentation, Thursday, 12, 1995, 9:20am - 6:30pm

## [102.01] Evidence for Another Black Hole Binary: X-ray Nova Ophiuci 1977

Ronald A. Remillard (MIT), Jeffrey E. McClintock (CFA), Jerome A. Orosz, Charles D. Bailyn (Yale)

We have conducted a productive campaign of spectral and photometric observations of the 'quiescent' optical counterpart of X-Nova Oph 1977 at CTIO during 1994 July. Five nights of photometry were analyzed to derive a binary period of 12.51 $\pm$ 0.03 hours. The light curve displays a typical double-wave pattern, with a modulation of $\pm$ 0.3 mag about the mean brightness, $V \sim 21.3$. Forty spectra were obtained with the 4 m telescope (2000 s each), complementing 13 similar observations performed at CTIO during 1993 May. Strong and broadened H$\alpha$ emission suggests that low-level accretion continues $\sim17$ years after X-ray outburst, similar to the behavior seen in the black hole binary, A0620-00. However, unusual changes in the emission-line profile in X-Nova Oph have occurred during 1993-94. The spectra were analyzed with 3 methods in the attempt to extract radial velocities of absorption lines from the secondary star, using cross correlations against seve! ral stars with G or K spectral ty