Long-Term Variability in the Quiescent X-Ray Transient V404 CYG

Abstract

We present the results of optical and infrared photometry of the quiescent X-ray transient V404 Cyg during the period 1992-2003.It is largely known that the Soft X-ray Transient (SXT) V404 Cyg exhibits short-term (sub-orbital) variations during quiescence (see eg. Pavlenko et al. 1996). It seems that fast variability during quiescence is not a peculiarity of V404 Cyg but a fingerprint of quiescent SXTs, irrespective of the nature of the compact object (Zurita, Casares & Shahbaz, 2003). Although these variations seem to originate in the accretion disc, the underlaying physical mechanism is not yet understood. Since V404 Cyg is the brightest SXT, and hence accessible with 1-m type telescopes, we embarked on a study of the fast variability over the period 1992-2003.