Abstract
The Cadmium–Zinc–Telluride Imager (CZTI) is an imaging instrument onboard AstroSat. This instrument operates as a nearly open all-sky detector above 60 keV, making possible long integrations irrespective of the spacecraft pointing. We present a technique based on the AstroSat-CZTI data to explore the hard X-ray characteristics of the \(\gamma \)-ray pulsar population. We report highly significant (\(\sim \)30\(\sigma \)) detection of hard X-ray (60–380 keV) pulse profile of the Crab pulsar using \(\sim \)5000 ks of CZTI observations within 5 to 70 \(\circ \) of Crab position in the sky, using a custom algorithm developed by us. Using Crab as our test source, we estimate the off-axis sensitivity of the instrument and establish AstroSat-CZTI as a prospective tool in investigating hard X-ray characteristics of \(\gamma \)-ray pulsars as faint as 10 mCrab.
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Acknowledgements
This publication makes use of data from the CZTI onboard Indian astronomy mission AstroSat, archived at the Indian Space Science Data Centre (ISSDC). The CZT Imager instrument was built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed and facilitated the project. We extend our gratitude to CZTI POC team members at IUCAA for helping with the augmentation of data. We thank Fermi Timing Observers Paul Ray and Kerr Mattew for their timely and favourable response in providing LAT ephemeris for Crab pulsar and helping with queries related to SSB polyco generation using tempo2. We thank the anonymous referee for his/her valuable suggestions to improve the paper. We would like to thank Avishek Basu, Karthik Rajeev and Atul Mohan for useful discussions. We thank IUCAA HPC facility where we carried out all the analysis. Anusree K. G. acknowledges support for this work from DST-INSPIRE Fellowship grant, IF170239, under Ministry of Science and Technology, India.
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This article is part of the Special Issue on “AstroSat: Five Years in Orbit”.
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Anusree, K.G., Bhattacharya, D., Rao, A.R. et al. AstroSat-CZTI as a hard X-ray pulsar monitor. J Astrophys Astron 42, 63 (2021). https://doi.org/10.1007/s12036-021-09707-5
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DOI: https://doi.org/10.1007/s12036-021-09707-5