Long Term X-ray Variability in GX13+1: Energy Dependent Periodic Modulation
arXiv:astro-ph/0306262 · doi:10.1086/377469
Abstract
A search is made for periodic modulation in the X-ray flux from the low mass X-ray binary GX13+1 using Rossi X-ray Timing Explorer All Sky Monitor data collected over a period of almost seven years. From a filtered data set, which excludes measurements with exceptionally large error bars and so maximizes signal to noise, modulation is found at a period of 24.065 +/- 0.018 days. The modulation is most clearly detectable at high energies (5 - 12 keV). Spectral changes are revealed as a modulation in hardness ratio on the 24 day period and there is a phase shift between the modulation in the 5 - 12 keV energy band compared to the 1.5 - 5 keV band. The high-energy spectrum of GX13+1 is unusual in displaying both emission and absorption iron line features and it is speculated that the peculiar spectral and timing properties may be connected.
Accepted for publication in ApJ. 21 pages including 9 figures