1993/01/08 by M. A. Abramowicz, G. Bao, V. Karas +1
Physics and Astronomy · #astro-ph
published as Astron.Astrophys. 272 (1993) 400-406 · 9 pages (14 figures not included), TeX, SISSA 220/92/A
arxiv created 1993/01/08 · arxiv updated 2009/12/01
The Seyfert galaxy NGC 6814 is known to show periodic variation of its X-ray luminosity. We found that the sequences of peaks (variability patterns) in the folded X-ray light curves constructed from the \it Exosat and \it Ginga data are remarkably similar when one ignores amplitudes of the peaks and considers only their phases. The stable pattern consists of five peaks which are present in the both curves. The phases of the corresponding peaks coincide with an accuracy of about 10 degrees. The probability that this coincidence occurs by chance is less than about 1% according to the most conservative estimate. The observed stable pattern of peaks may be produced by a stable distribution of ``bright spots'' on the accretion disk surface, \it e.g. by strong vortices or magnetic flux tubes.