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      Permanent link:
      https://www.ias.ac.in/article/fulltext/joaa/042/0037

    • Keywords

       

      AstroSat; CZT Imager; cosmic rays; detectors: X-rays; detectors: noise.

    • Abstract

       

      The Cadmium–Zinc–Telluride (CZT) Imager on board AstroSat is a hard X-ray imaging spectrometer operating in the energy range of 20–100 keV. It also acts as an open hard X-ray monitor above 100 keV capable of detecting transient events like the Gamma-ray Bursts (GRBs). Additionally, the instrument has thesensitivity to measure hard X-ray polarization in the energy range of 100–400 keV for bright on-axis sources like Crab and Cygnus X-1 and bright GRBs. As hard X-ray instruments like CZTI are sensitive to cosmic rays in addition to X-rays, it is required to identify and remove particle induced or other noise events and select events for scientific analysis of the data. The present CZTI data analysis pipeline includes algorithms for such event selection, but they have certain limitations. They were primarily designed for the analysis of data from persistent X-ray sources where the source flux is much less than the background and thus are not best suited for sources like GRBs. Here, we re-examine the characteristics of noise events in CZTI and present a generalized event selectionmethod that caters to the analysis of data for all types of sources. The efficacy of the new method is reviewed by examining the Poissonian behavior of the selected events and the signal to noise ratio for GRBs.

    • Author Affiliations

       

      A. RATHEESH1 2 3 A. R. RAO1 4 N. P. S. MITHUN5 S. V. VADAWALE5 A. VIBHUTE4 D. BHATTACHARYA4 P. PRADEEP6 S. SREEKUMAR6 V. BHALERAO7

      1. Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India.
      2. Department of Physics, Tor Vergata University of Rome, Via della Ricerca Scientifica 1, 00133 Rome, Italy.
      3. INAF - IAPS, Via Fosso del Cavaliere 100, 00133 Rome, Italy.
      4. Inter University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007, India.
      5. Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, India.
      6. Vikram Sarabhai Space Centre, Kochuveli, Thiruvananthapuram 695 022, India.
      7. Indian Institute of Technology Bombay, Mumbai 400 076, India.
    • Dates

       
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