We present the results of a study with the Swift Burst Alert Telescope in the 14 - 195 keV range of the long-term variability of 5 low mass X-ray binaries with reported or suspected super-orbital periods -- 4U 1636-536, 4U 1820-303, 4U 1916-053, Cyg X-2 and Sco X-1. No significant periodic modulation was detected around the previously reported values in the 4U 1916-053, Cyg X-2 or Sco X-1 light curves. The ∼170 d period of 4U 1820-303 was detected up to 24 keV, consistent with the proposed triple system model. The ∼46 d period in 4U 1636-536 was detected up to 100 keV, clearly inconsistent with variable photoelectric absorption via a warped precessing disc. We speculate that the appearance of this modulation after 4U 1636-536 entered the low/hard state indicates that this variability could be linked to jet precession such as observed in SS 433.
@article{arxiv.0807.1616,
title = {A Swift BAT Look at Super-Orbital X-ray Binaries},
author = {Sean A. Farrell and Didier Barret and Gerald Skinner},
journal= {arXiv preprint arXiv:0807.1616},
year = {2010}
}
Comments
3 pages, 1 figure, published in proceedings of the conference "A Population Explosion: The Nature & Evolution of X-ray Binaries in Diverse Environments", St Petersburgh Beach, Florida, 28th Oct - 2nd Nov 2007