Abstract
CCD photometry of the black hole candidate GRO J0422+32 in quiescence, obtained
at Haute-Provence from 1994 November to 1995 February, reveals a double-wave
modulation at a period close to the value we found during outbursts and also
close to one of the possible periods derived by Filippenko, Matheson and Ho
(1995) from spectroscopic observations with the W. M. Keck 10-m telescope. A
period of 0.212140 ± 0.000003 d (5.09136 ± 0.00007 h) fits all our
photometric data from 1993 January to 1995 February and yields a minimum in our
light curves at the inferior conjunction of the M star, as determined from the
radial velocity data of Filippenko et al. (1995) The quiescent Rc-band light
curve exhibits a changing asymmetry of shape and a variable amplitude. On two
consecutive nights the source was found constant to within ± 0.05 mag,
suggesting an upper limit on the ellipsoidal effect in this band.
Key Words: accretion : accretion disks -- binaries : close --
stars
: individual (GRO J0422+32) -- X-rays : stars