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    • An alternative scheme to estimate AstroSat/LAXPC background for faint sources

      RANJEEV MISRA JAYASHREE ROY J. S. YADAV

      SCIENCE RESULTS Volume 42 Published: 24 June 2021 Article ID 0055

    • Fulltext

       

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      Permanent link:
      https://www.ias.ac.in/article/fulltext/joaa/042/0055

    • Keywords

       

      AstroSat/LAXPC; instrument background; calibration.

    • Abstract

       

      An alternative scheme is described to estimate the layer 1 LAXPC 20 background for faint sources where the source contribution to the 50–80 keV count rate is less than 0.25 counts/s (15 milli-crabs or $6\times 10^{-11}$ ergs/s/cm$^2$). We consider 12 blank sky observations and based on their 50–80 keV count rate in 100 second time-bins, generate four template spectra which are then used to estimate the background spectrum and lightcurve for a given faint source observation. The variance of the estimated background subtracted spectra for the 12 blank sky observations is taken as the energy dependent systematic uncertainty which will dominate over the statistical one for exposures longer than 5 ks. The estimated 100 second time bin background lightcurve in the 4–20 keV band with a 3% systematic error matches with the blank sky ones.The 4–20 keV spectrum can be constrained for a source with flux $\gtrapprox$1 milli-crab. Fractional rms variability of 10% can be determined for a $\sim$5 milli-crab source lightcurve binned at 100 seconds. To illustrate the scheme, the lightcurves and spectra of three different blank sky observations, three AGN sources (Mrk 0926, Mrk 110, NGC 4593) and LMC X-1 are shown.

    • Author Affiliations

       

      RANJEEV MISRA1 JAYASHREE ROY1 J. S. YADAV2

      1. Inter-University Centre for Astronomy and Astrophysics, Pune 411 007, India.
      2. Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208 016, India.

    • Dates

       
      Published
      24 June 2021
      Manuscript received
      5 November 2020
      Accepted
      11 February 2021
      Final version published online
      24 June 2021

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