Abstract Details
| Name: Tanmoy Chattopadhyay Affiliation: Pennsylvania State University, USA Conference ID: ASI2019_320 Title : Observational Aspects of Hard X-ray Polarimetry Authors and Co-Authors : Tanmoy Chattopadhyay (Penn State), S. V. Vadawale (PRL), A. R. Rao (TIFR), Dipankar Bhattacharya (IUCAA), team members of AstroSat-CZTI Abstract Type : Invited Abstract Category : Thesis Abstract : CZT Imager onboard AstroSat is primarily a hard X-ray spectroscopic instrument but provides sensitive polarization measurements in the energy range of 100 – 300 keV. Crab and Cygnus X-1 are the two potential targets for CZTI polarimetry. With an accumulated 800 ks of observation, CZTI provided till date statistically the most significant polarization measurement for Crab (32% for all-Crab and 40% for the off-pulse). Phase resolved polarimetry of the pulsed radiation of Crab has also been attempted for the first time in X-rays. Another important characteristic of CZTI is the increasing transparency of the support structure in hard X-rays, which enables it to function as a wide field hard X-ray monitor providing an unique opportunity for GRB detection and polarization measurement. In a sample of 50 GRBs detected by CZTI in 1 year after the launch, we attempted polarization measurement for 11 bright GRBs. A large sample of such polarization measurements is supposed to shed more light into the emission mechanism of GRB prompt emission. Currently, we are implementing a few new techniques in the polarization analysis to improve the sensitivity of the instrument for both ON and OFF-axis sources. These techniques enable polarization measurement all the way to 600 keV, which is critical for BH X-ray binaries like Cygnus X-1 to resolve the mystery of corona vs jet origin of X-rays beyond 100 keV. I would briefly present the basics of CZTI polarimetry along with the new techniques and the recent findings. |