Session 17. X-ray Binaries III
Poster, Sunday-Wednesday, March 23, 2003, Duration of Meeting

[17.17] X-ray Bursts in Neutron Star and Black Hole Binaries from USA Data: Detections and Upper Limits

D. Tournear, E. Raffauf, E. D. Bloom, W. Focke, B. Giebels, G. Godfrey, P. M. Saz Parkinson, K. T. Reilly, G. Shabad (Stanford Linear Accelerator Center), P. S. Ray, K. S. Wood, M. T. Wolff, R. M. Bandyopadhyay, G. Fritz, P. Hertz, M. P. Kowalski, M. N. Lovellette, D. J. Yentis (Naval Research Laboratory), J. D. Scargle (NASA Ames Research Center)

Type I X-ray bursts are believed to be caused by unstable burning on the surface of a neutron star in a binary system. In this paper we examine the Unconventional Stellar Aspect (USA) experiment archive of binary neutron star and Black Hole Candidate (BHC) data for evidence of X-ray bursts. We scanned 927.5 ks of neutron star data and found 19 Type I X-ray bursts, yielding an average burst rate \lambda = 2.05\times10-2 bursts/ks, or 48.8 ks between bursts. We scanned 972.3 ks of BHC data and found no evidence for X-ray bursts, yielding a 95% confidence limit of \leq 3.1\times10-3 bursts/ks, or >325 ks between bursts, on the rate of X-ray bursts in BHCs. We discuss how this provides evidence against the presence of a surface on the compact object in these systems.\\ \\ Work at SLAC was supported by Department of Energy contract DE-AC 03-76-SFO0515. Basic research in X-ray astronomy at the Naval Research Laboratory is supported by ONR/NRL. This work was also supported by the NASA Applied Information Systems Research Program.