AN UPPER LIMIT TO THE MASS OF THE BLACK-HOLE IN V404 CYGNI

We have measured the II-band light curve of the black hole binary V404 Cyg (=GS 2023+338). When folded at the spectroscopic orbital period, 6.4714 days, the light curve has two maxima and two minima per orbit a nd a peak-to-peak amplitude of similar to 0.25 mag. This variation is produced primarily by ellipsoidal variations of the KO IV star in the system, but the light curve is distorted by other sources of variabili ty as well. Because of the distortions and because of an unknown contr ibution to the infrared flux from the accretion disk around the black hole, analysis of the ellipsoidal variations yields only a lower limit to the orbital inclination of V404 Cyg and, thus, an upper limit to t he mass of its black hole. Our analysis of the H-band light curve yiel ds an upper limit of 12.5 M(.). We show that previously published K-ba nd light curves of V404 Cyg were probably also contaminated by other s ources of variability. Reanalysis of the K-band data gives results con sistent with the H-band data.