Fast optical variability of GRO J0422+32

Abstract

We present spectroscopic and photoelectric optical observations of the X-ray nova GRO J0422+32 = Nova Persei 1992 obtained with a TV spectrum scanner, UBVR photometer and soft/hardware MANIA (Multichannel Analysis of Nanoseconds Intensity Alterations) complex on the Special Astrophysical Observatory 6 m telescope and with a fast double-head photometer at the Bologna Observatory. In the early phase after discovery the spectrum of the object presented a variable continuum with intensity rising blueward and some weak emissions (H, HE, N). Photoelectric data show a modulation on a time scale of about 5 hours and stochastic flashes, probably of nonthermal origin, on a timescale from 10-20 ms to 200 s. A unique episode of fading of the object was observed on JD 2448986.52.