Wide-Field X-Ray Monitor for Hete-Ii

The re-flight of the High Energy Transient Explorer (HETE) is scheduled in 1999. The Wide-field X-ray Monitor (WXM) is one of the two X-ray detector systems on HETE employed for localizing gamma-ray bursts in real time. It has larger effective area and thus is more sensitive to weaker bursts than the Soft X-ray Camera (SXC), the other position-sensitive instrument which uses CCDs to achieve finer resolution. WXM consists of four Xe-filled 1-D position-sensitive proportional counters, two in the X-direction and two in the Y-direction. The proportional counters and electronics are provided by RIKEN and Miyazaki University, while the coded aperture and on-board localization software is provided by Los Alamos National Laboratory. It is sensitive to X-rays between 2 keV and 25 keV, and is expected to localize gamma-ray bursts with ∼ 10′ accuracy. We report the preparation status of the hardware, and present the expected performance of WXM.