AstroFIt 2 – COFUND fellow since July 1, 2019
Project ended 30 June, 2020
INAF Research Centre: Osserbatorio di Astrofisica e Scienze dello Spazio
Email: rupal.basak at inaf.it
Papers/Publications:
- Prompt Emission Polarimetry of Gamma-Ray Bursts with the AstroSat CZT Imager (The Astrophysical Journal, 17/10/2019)
- Peculiar Prompt Emission and Afterglow in the H.E.S.S.-detected GRB 190829A (The Astrophysical Journal, 21/07/2020)
Project title: GRBRad – GRB radiation: physical mechanisms, correlations and constraining cosmological parameters
Abstract:
GRBs are the most intense cosmological explosions marking the death of massive stars or coalescing black hole or neutron star binaries. Being very luminous and visible out to high readshift ~9, they are of high interest also for cosmology and fundamental physics. Their intensity and peak energy of νFν spectrum (Ep,i) follow a universal correlation which indicates an underlying basic radiation process. This project aims to (A) understand the radiation mechanism and (B) study Ep,i-intensity correlation, its physical origin and its effectiveness in using GRBs for measuring cosmological parameters. To this end, we shall obtain multiwavelength data ranging from γ-ray to X-ray and optical wavelength. In parallel, we shall simulate the spectrum emerging from a GRB jet to directly fit the data for the first time. In recent papers, we have found in some cases that the spectrum can be fitted with two blackbodies and a powerlaw and can be explained as emerging from a jet with a lateral structure. We will test this model and its variants against the multiwavelength data. Based on our understanding, we will then study Ep,i-intensity correlation and derive cosmological parameters. Our project is particularly timely with Swift and Fermi providing valuable data. In addition, we will have access to the proprietary data of ASTROSAT/CZTI that will provide important polarization measurement. With our existing collaboration in Italy and Poland, we shall also obtain optical data from HST and VLT, very high energy data from H.E.S.S. and X-ray data from NuSTAR and Chandra.
The recent detection of two gravitational wave events from merging black holes has opened up a new era of our understanding of GRBs. But, finding the electromagnetic counterpart is one key aspect to draw a detailed inference about the process. With advanced LIGO and VIRGO more such events will be detected. Then the results obtained in our project will be invaluable providing an important and complementary view of GRBs.