Astronomy and Astrophysics Seminars

Luminosity function of long Gamma Ray Bursts

by Mr. Debdutta Paul (DAA - TIFR)

Tuesday, April 11, 2017 from to (Asia/Kolkata)
at DAA SEMINAR ROOM ( A269 )
TIFR
Description
The “Luminosity function” of Gamma Ray Bursts (GRBs) is an important, but difficult, quantity to measure. The lack of good flux limited sample with known distances is one of the main problems. One of the methods used to increase the sample is to  construct “pseudo-redshifts” of GRBs from the well-known Yonetoku correlation. In this study, I will present an analysis of the most recent dataset that allows us to take a re-look at the parameters of this correlation. I will show that the method fails to predict the redshifts of individual GRBs accurately, although it is statistically reliable, justifying the use of the pseudo-redshifts for the study of Luminosity functions. Preliminary efforts to understand the discrepancies will also be presented. I will use the most statistically reliable parameters of the Yonetoku correlation that are derived from this study, to constrain the Luminosity function of long GRBs, using the most updated estimates of the cosmic star-formation rates. The limitations of measuring pseudo-redshifts and the need for a good sample of bright GRBs with measured redshifts are highlighted. The derived Luminosity function can be used to   determine the number of GRBs observed by a GRB-detector. Using this, I demonstrate that the CZT Imager of AstroSat will help in getting a complete sample of bright GRBs. The localization capability of CZT Imager is investigated, using the test case of GRB 151006A, and the method to improve this localization is discussed. It is emphasised that by a quick localization, a good sample of bright GRBs with measured redshifts can be obtained.