Name: Anusree K G
Affiliation: Mahatma Gandhi University
Conference ID : ASI2022_80
Title : Pulsars in AstroSat-CZTI: Detection in sub-MeV bands & Estimation of Spectral Index from Hardness Ratios
Authors : Anusree, K.G., Bhattacharya, D., Bhalerao, V. & Anumarlapudi, A.
Abstract Type: Poster
Abstract Category : Stars, ISM and Galaxy
Abstract : The Cadmium Zinc Telluride Imager (CZTI) onboard AstroSat, an open detector above∼100 keV, is a prospective tool in investigating the hard X-ray characteristics of γ-ray pulsars. A custom algorithm detects pulsars from long integration(∼years) of archival data. Nearly 20% of the total pixels in CZTI were excluded from such analysis due to their inadequate spectral behaviour (low-gain). However, a recent re-calibration of such pixels indicate higher energy thresholds. This work includes these pixels and extends the pulsar detection in CZTI to ∼1 MeV. By observing the well-known morphology of Crab pulse profiles up to ∼1 MeV, we verify the new gains of these pixels from the latest calibration. However, the pulsar spectra obtained from the long integration of CZTI data is poor for any standard spectral analysis. We use the instrument responses based on the AstroSat Mass Model simulations together with the hardness ratios observed in CZTI to predict the power-law photon index of a pulsar’s spectrum, assuming it is close to a power law in the CZTI band. We present our results for the phase-resolved spectrum of PSR J0534+2200 and the total pulsed spectrum of PSR J1513-5908 and PSRJ0835-4510 and show that the estimated photon indices are more than 85% accurate