Abstract Details
| Name: AJAY Affiliation: RATHEESH Conference ID: ASI2018_1672 Title : Astrosat Cadmium Zinc Telluride Imager as a Short GRB Detector Authors and Co-Authors : Ajay Ratheesh (1), Debdutta Paul (1), A R Rao (1), D. Bhattcahrya (2), Ajay Vibhute (2), S.V. Vadawale (3), V.B. Bhalerao (4) 1-Tata Institute of Fundamental Research, Mumbai 2-Inter Universities Center for Astronomy and Astrophysics, Pune 3-Physical Research Laboratory, Ahmedabad 4-Indian Institute of Technology, Mumbai Abstract Type : Contributed Talk Abstract Category : Instrumentation and Techniques Abstract : Detection of a short GRB170817A along side GW170817 from a neutron star (NS) merger has prompted the search for similar short GRBs. Characterizing these short GRBs will not only give insight into the science of NS-NS mergers, but also the rate of occurrence of such events. Searching for these events is difficult as they exist in shorter time scales where fluctuations in the detector data due to Cosmic Ray interactions and other noise events are dominant. Hence characterising and excluding the noise events are important in the search for short GRBs. Cadmium Zinc Telluride Imager onboard Astrosat, being comparatively less prone to charge particle background due to its low inclination orbit, with pixelated detectors, and an open detector above 100 keV, can a be an effective short GRB detector if the noise sources in the detector are understood and eliminated. Here we present the results of an attempt to understand the noise characteristics by developing an algorithm to detect and eliminate various sources of noise in Astrosat CZTI. CZTI consists of pixelated CZT detectors, which are triggered by individual photons, and records each such ‘event’ separately. However, the detectors are also prone to triggers from other sources, cosmic rays and thermal instabilities being amongst them, termed as ‘noise’ events. Here we examine the properties of all CZT events, to segregate genuine events by astrophysical photons from noise. We look into the events at different time scales. Since the individual detectors are equipped with fast and sensitive amplifiers to cater to high count rates, they trigger multiple times for large charge deposition from Cosmic Rays. It is found that the heavy charge deposition induces crystal defects in the detector, which can trigger noise events up to 200 ms after a Cosmic Ray interaction. The proposed algorithm eliminates all noise events and hence improves the sensitivity of the instrument to detection of transients like Gamma Ray Bursts, in addition to producing cleaned data of the observed astrophysical sources. |