AstroSat-CZTI as a hard X-ray Pulsar Monitor

TL;DR

This paper demonstrates how AstroSat-CZTI can be used as a sensitive all-sky hard X-ray monitor to detect and analyze gamma-ray pulsars, exemplified by the Crab pulsar observation.

Contribution

It introduces a new technique for using CZTI data to study hard X-ray pulsar properties and establishes the instrument's potential for faint gamma-ray pulsar detection.

Findings

Detected Crab pulsar's hard X-ray pulse profile with high significance

Estimated the off-axis sensitivity of AstroSat-CZTI for pulsar observations

Showed CZTI can detect gamma-ray pulsars as faint as 10 mCrab

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 degrees 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.