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Using collimated CZTI as all-sky X-ray detector based on Earth occultation technique

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Abstract

All-sky monitors can measure the fluxes of astrophysical sources by measuring the changes in observed counts as the source is occulted by the Earth. Such measurements have typically been carried out by all-sky monitors like CGRO-BATSE and Fermi-GBM. We demonstrate for the first time the application of this technique to measure fluxes of sources using a collimated instrument: the Cadmium Zinc Telluride detector on AstroSat. Reliable flux measurements are obtained for the Crab nebula and pulsar, and for Cyg X–1 by carefully selecting the best occultation data sets. We demonstrate that CZTI can obtain such measurements for hard sources with intensities \(\gtrsim \)1 Crab.

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Notes

  1. CZTI pipeline: http://astrosat-ssc.iucaa.in/?q=cztiData.

  2. The fraction 0.417 = 5/12 comes from backward compatibility during code development.

  3. https://swift.gsfc.nasa.gov/results/transients/BAT_current.html#anchor-CygX-1.

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Acknowledgements

We thank Vedant Shenoy and Akash Anumarlapudi for their assistance in data analysis. CZT–Imager is built by a consortium of Institutes across India. The Tata Institute of Fundamental Research, Mumbai, led the effort with instrument design and development. Vikram Sarabhai Space Centre, Thiruvananthapuram provided the electronic design, assembly and testing. ISRO Satellite Centre (ISAC), Bengaluru provided the mechanical design, quality consultation and project management. The Inter University Centre for Astronomy and Astrophysics (IUCAA), Pune did the Coded Mask design, instrument calibration, and Payload Operation Centre. Space Application Centre (SAC) at Ahmedabad provided the analysis software. Physical Research Laboratory (PRL) Ahmedabad, provided the polarisation detection algorithm and ground calibration. A vast number of industries participated in the fabrication and the University sector pitched in by participating in the test and evaluation of the payload. The Indian Space Research Organisation funded, managed and facilitated the project. This work utilised various software including Python, AstroPy (Robitaille et al. 2013), NumPy (van der Walt et al. 2011), and Matplotlib (Hunter 2007).

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Authors and Affiliations

  1. Indian Institute of Technology Bombay, Mumbai, 400 076, India

    Akshat Singhal, Rahul Srinivasan & Varun Bhalerao

  2. Université Côte d’Azur, Nice, France

    Rahul Srinivasan

  3. The Inter-University Centre for Astronomy and Astrophysics, Pune, 411 007, India

    Dipankar Bhattacharya

  4. Tata Institute of Fundamental Research, Mumbai, 400 005, India

    Rahul Srinivasan & A. R. Rao

  5. Physical Research Laboratory, Ahmedabad, 380 009, India

    Santosh Vadawale

  6. CNRS, Nice, France

    Rahul Srinivasan

  7. Laboratoire Lagrange, Nice, France

    Rahul Srinivasan

  8. Laboratoire Artémis, Nice, France

    Rahul Srinivasan

Authors
  1. Akshat Singhal
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  2. Rahul Srinivasan
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  3. Varun Bhalerao
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  4. Dipankar Bhattacharya
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  5. A. R. Rao
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  6. Santosh Vadawale
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Corresponding author

Correspondence to Akshat Singhal.

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This article is part of the Special Issue on “AstroSat: Five Years in Orbit”.

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Singhal, A., Srinivasan, R., Bhalerao, V. et al. Using collimated CZTI as all-sky X-ray detector based on Earth occultation technique. J Astrophys Astron 42, 64 (2021). https://doi.org/10.1007/s12036-021-09743-1

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  • DOI: https://doi.org/10.1007/s12036-021-09743-1

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