Development of a New Detector for Hard X-Ray Observations of Non-Thermal Emission from Low-Mass X-Ray Binaries
Abstract
The focus of this work is the development of a new balloon-borne hard X-ray telescope, EXITE2. It uses a coded-aperture mask giving 22 arcmin resolution and a 4.65^circ field of view. The telescope incorporates a phoswich detector that operates in the 20-600 keV range. It will be used to look for hard X-ray tails from low-mass X-ray binaries. There are models that predict that such tails should be produced by non -thermal processes in these accreting systems, and thus observations could shed light on the inner workings of these systems. I first summarize the models and observations, concluding that EXITE2 could put interesting limits on power-law tails that have been observed from the few burster sources to date. In the second chapter, I discuss the design requirements, and in Chapter 3, I describe the EXITE2 detector system. In Chapter 4, I focus on the effects of distortions or background variations, and the calibration system which we have developed to minimize distortions. In Chapter 5, I describe the preliminary flight results: a background of {~}4times10 ^{-4} photons rm cm^{-2} s^{-1} keV^{-1} at 100 keV, showing that the addition of an imaging capability to a phoswich for the first time does not harm the background rejection. Chapter 6 describes analysis of EXITE1 data on the X-ray binary Her X-1. Chapter 7 contains EGRET and COMPTEL observations, setting the best limits yet on gamma -ray emission from the millisecond pulsars that the two globular clusters we observed may contain, including limits in the COMPTEL energy band (just above the EXITE2 band). Chapter 8 contains analysis of observations by Ginga (in the energy band just below that of EXITE2) of X1916-053, a burster. The timing analysis severely constrains one model of the dips, and the spectral analysis shows that the power-law-like emission at lower energies can continue above 10 keV. Thus the source should be studied at higher energies, with a detector such as EXITE2.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- January 1995
- Bibcode:
- 1995PhDT........10M
- Keywords:
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- NEUTRON STARS;
- Physics: Astronomy and Astrophysics