Eclipse Timings of the Transient Low Mass X-ray Binary EXO0748-676. IV. The Rossi X-Ray Timing Explorer Eclipses

摘要

We report our complete database of X-ray eclipse timings of the low massX-ray binary EXO0748-676 observed by the Rossi X-Ray Timing Explorer (RXTE)satellite. As of this writing we have accumulated 443 full X-ray eclipses, 392of which have been observed with the Proportional Counter Array on RXTE. Theseinclude both observations where an eclipse was specifically targeted and thoseeclipses found in the RXTE data archive. Eclipse cycle count has beenmaintained since the discovery of the EXO0748-676 system in February 1985. Wedescribe our observing and analysis techniques for each eclipse and describeimprovements we have made since the last compilation by Wolff et al. (2002).The principal result of this paper is the database containing the timingresults from a seven-parameter fit to the X-ray light curve for each observedeclipse along with the associated errors in the fitted parameters. Based on thestandard O-C analysis, EXO0748-676 has undergone four distinct orbital periodepochs since its discovery. In addition, EXO0748-676 shows small-scale eventsin the O-C curve that are likely due to short-lived changes in the secondarystar.