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Cosmological Distributions and Evolution of Gamma-ray Bursts and Their Relation to Star Formation Rate and Gravitational Waves

Speaker:Prof. Vahé Petrosian
Affiliation:Physics Department and Department of Applied Physics,
Stanford University
Date:April 30, 2018 (Monday)
Time:10:30 a.m.
Venue:Room 522, 5/F, Chong Yuet Ming Physics Building, HKU


Gamma-ray Bursts (GRBs), by virtue of their large redshifts are good candidates for probing the early universe, in particular the history of star formation rate (SFR). There have also been several attempts to use GRBs as "standard candles" for measurements of the global cosmological parameters. The achievement of these potentials requires determination of their "luminosity function" and the cosmological evolutions of their luminosities and formation rate (GRBFR). This is normally done by a forward fitting of the data to some assumed parametric model prediction, often assuming a GRBFR formation rate similar to the SFR. However, recent applications of the non-parametric methods developed by Efron and Petrosian to long GRBs by several authors have consistently shown (i) presence of strong luminosity evolution, which makes their use as standard candles problematical, and (ii) a GRBFR that deviates from SFR significantly at low redshifts. If this is also true for short GRBs, whose progenitors are believed to be neutron star-neutron star or neutron star black hole mergers, it will have profound implications for the rate and evolution of gravitational wave sources. I will describe the results on long GRBs and the potentials of short GRBs.

Coffee and tea will be served 20 minutes prior to the seminar.

Anyone interested is welcome to attend.