Bibcode
Pavlenko, E. P.; Martin, A. C.; Casares, J.; Charles, P. A.; Ketsaris, N. A.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 281, Issue 3, pp. 1094-1104.
Advertised on:
8
1996
Citations
28
Refereed citations
24
Description
We present 2 weeks of CCD photometry of V404 Cyg, the optical
counterpart of the soft X-ray transient (SXT) GS 2023+338, taken from La
Palma in 1992 July. The R-band light curve shows a clear 0.3-mag
ellipsoidal modulation on the estabished 6.5-d orbital period, but with
substantial (up to 0.3 mag) superposed variations that occur during each
night on a time-scale of 6 h. We model both the mean orbital light curve
and its lower envelope (which we presume to show the secondary star with
minimum contamination from the accretion disc). With a mass ratio
already known from the optical spectroscopy of Casares & Charles,
the analysis of the lower envelope light curve leads to an orbital
inclination of i=56 deg+/-2 deg. Our best model requires no hotspot
contribution. The shorter time-scale of variability is consistent with
the 6-h quasi-periodicities that have been seen in outburst and during
the early quiescent period. Using periodogram analysis, we find three
components of the 6-h peak (at 5.90, 6.07 and 6.24 h). The periodograms
show the outside peaks to be stronger than the smaller, central peak. A
peak in the power spectrum at 4.5 d coincides with the beat period of
these outside peaks. The nature of these periodicities is unknown.