Abstract
ASTROSAT is India’s first satellite fully devoted to astronomical observations covering a wide spectral band from optical to hard X-rays by a complement of 4 co-aligned instruments and a Scanning Sky X-ray Monitor. One of the instruments is Large Area X-ray Proportional Counter with 3 identical detectors. In order to assess the performance of this instrument, a balloon experiment with two prototype Large Area X-ray Proportional Counters (LAXPC) was carried out on 2008 April 14. The design of these LAXPCs was similar to those on the ASTROSAT except that their field of view (FOV) was 3 ∘ × 3 ∘ versus FOV of 1 ∘ × 1 ∘ for the LAXPCs on the ASTROSAT. The LAXPCs are aimed at the timing and spectral studies of X-ray sources in 3-80 keV region. In the balloon experiment, the LAXPC, associated electronics and support systems were mounted on an oriented platform which could be pre-programmed to track any source in the sky. A brief description of the LAXPC design, laboratory tests, calibration and the detector characteristics is presented here. The details of the experiment and background counting rates of the 2 LAXPCs at the float altitude of about 41 km are presented in different energy bands. The bright black hole X-ray binary Cygnus X-1 (Cyg X-1) was observed in the experiment for ∼ 3 hours. Details of Cyg X-1 observations, count rates measured from it in different energy intervals and the intensity variations of Cyg X-1 detected during the observations are presented and briefly discussed.
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Acknowledgments
We are extremely grateful to the engineering and technical staff of TIFR Workshop who carried out fabrication of major parts of LAXPCs and gondola system of the instrument. We express our sincere thanks to the TIFR Balloon Facility staff under the supervision of Mr S. Sreenivasan who carried out all the balloon flight related operations in an excellent manner. It is a pleasure to acknowledge the help of Prof H. M. Antia of TIFR in generating detector response matrix. We are grateful to late Mr. M.R.Shah and Mr. K. Kutty for their contributions to the orientation system and its fabrication used in this experiment. This research was in part supported by NASI that awarded Senior Scientist Fellowship to P. C. Agrawal. We also thank the anonymous referee for their suggestions which improved the manuscript.
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Roy, J., Agrawal, P.C., Dedhia, D.K. et al. Performance of large area x-ray proportional counters in a balloon experiment. Exp Astron 42, 249–270 (2016). https://doi.org/10.1007/s10686-016-9508-z
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DOI: https://doi.org/10.1007/s10686-016-9508-z