11 March 2003 In-orbit performance of wide-field x-ray monitor on HETE-2
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The Wide-field X-ray Monitor (WXM) is one of the scientific instruments carried on the High Energy Transient Explorer 2 (HETE-2) satellite launched in October 2000. The WXM consists of three elements: (1) four identical Xe-filled one-dimensional position-sensitive proportional counters, two in the spacecraft X-direction and two in the Y-direction, (2) two sets of one-dimensional coded apertures orthogonally mounted above the counters in the X and Y-direction, and (3) the main electronics that processes analog signals from the counters. The WXM counters are sensitive to X-rays between 2 keV and 25 keV within a field-of-view of about 1.5 sr with a total detector area of about 350 cm2. The combination of the apertures and the counters provides GRB locations with accuracy ~10 arcmin. The counters and electronics are developed and fabricated by RIKEN, and the apertures and on-board software are designed and provided by Los Alamos National Laboratory. The WXM plays a major roll in the GRB localization and its spectroscopy in the energy range between 2 keV and 25 keV. During the first year of observations, a number of steady X-ray sources as well as high-energy transients were detected with the WXM. Observing Crab nebula and Sco X-1, we have calibrated the detector alignment between the WXM and the optical camera system with 2 arcmin accuracy. As of 29 July 2002, nineteen GRBs have been localized with the WXM in the 18 months of stable operations. Twelve of them were reported to the GCN within a delay of 10 hours, and 4 optical transients were identified by ground based telescopes. The energy response of the detectors has also been calibrated using the Crab spectrum. We report the in-orbit performance of the WXM instrument during the first 18 months.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yuji Shirasaki, Nobuyuki Kawai, Atsumasa Yoshida, Toru Tamagawa, Ken'ichi Torii, Takanori Sakamoto, Masaru Matsuoka, Edward E. Fenimore, Mark C. Galassi, Donald Q. Lamb, Carlos Graziani, Tim Q. Donaghy, Roland K. Vanderspek, Makoto Yamauchi, Kunio Tagagishi, Isamu Hatsukade, "In-orbit performance of wide-field x-ray monitor on HETE-2", Proc. SPIE 4851, X-Ray and Gamma-Ray Telescopes and Instruments for Astronomy, (11 March 2003); doi: 10.1117/12.461414; https://doi.org/10.1117/12.461414


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