Search for Hard X-Ray Emission from the Soft X-Ray Transient Aquila X-1

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Session 102 -- X-Ray Variables, Binaries and Transients
Display presentation, Thursday, 12, 1995, 9:20am - 6:30pm

[102.07] Search for Hard X-Ray Emission from the Soft X-Ray Transient Aquila X-1

B.A. Harmon (NASA/MSFC), S.N. Zhang (USRA), W.S. Paciesas (UAH), M. Tavani, P. Kaaret, E. Ford (CU)

We are investigating the possibility of hard x-ray emission from the recurrent soft x-ray transient and x-ray burst source Aquila X-1 (Aql~X-1). Outbursts of this source are relatively frequent with a spacing of $\sim$4-10 months (Kitamoto, S. et al. 1993, ApJ, 403, 315). The recent detections of hard tails (\(>\)20 keV) in low luminosity x-ray bursters (Barret, D. \& Vedrenne, G. 1994, ApJ Supp. S. 92, 505) suggest that neutron star transient systems such as Aql~X-1 can produce hard x-ray emission which is detectable by BATSE . We are correlating reported optical and soft x-ray observations since 1991 of Aql~X-1 with BATSE observations in order to search for hard x-ray emission episodes, and to study their temporal and spectral evolution. We will present preliminary results of this search in the 20-1000 keV band using the Earth occultation technique applied to the large area detectors. If this work is successful, we hope to alert the astronomical community for the next Aql~X-1 outburst expected in 1995. Simultaneous x-ray/hard x-ray and optical observations of Aql~X-1 during outburst would be of great importance for the modeling of soft x-ray transients and related systems.

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