Conveners
Transients and Gamma-Ray Bursts II: Gamma-Ray Bursts
- Markus Boettcher (North-West University)
We study the narrowest spectra expected from GRBs. We present an analytical function for the spectrum that is emitted from the photosphere of a radiation-dominated flow that is under acceleration. We also present numerical spectra from photospheres occurring during the transition into the coasting phase of the flow. Using these spectral models, we reanalyse Fermi observations of GRB100507 and...
In the era of multi-messenger astronomy, all-sky surveys of transient events serve an important role to provide detection and location information to follow-up instruments. The Fermi-GBM serves as the dominant gamma-ray transient detector with coverage of the entire unocculted sky. We introduce a new method to improve both the precision and accuracy of the Fermi-GBM’s ability to locate...
In this catalog, we present the results of a systematic study of 150 gamma-ray bursts (GRBs) with reliable redshift estimates detected in the triggered mode of the Konus-Wind (KW) experiment. The sample covers the period from 1997 February to 2016 June and represents the largest set of cosmological GRBs studied to date over a broad energy band. We provide the burst durations, the spectral...
In preparation for the Second LAT Gamma-Ray Burst (GRB) catalog, we explore the use
of the LAT low-energy (LLE) data selection to detect bursts with gamma-ray energy below 100 MeV. Here we present the sample of GRBs that are detected at these energies
through a Bayesian Block analysis of all Fermi Gamma-ray Burst Monitor (GBM)
triggers collected in 8 years of Fermi mission.
In particular,...
We analyze the prompt emission of two of the brightest Gamma-Ray Bursts (GRBs) observed by Fermi at MeV energies but surprisingly faint at > 100 MeV energies. Time-resolved spectroscopy reveals a sharp high-energy cutoff. We first characterize phenomenologically the cutoff and its time evolution. We then fit the data to two models where the high-energy cutoff arises from intrinsic opacity to...
The magnetization of gamma-ray burst jets is one of the most important unanswered questions to-date, as it would help to constrain the progenitor, the emission mechanism(s) and the central engine of GRBs. In my talk, I explain how observables can set constraints on models of magnetized jets in the framework of photospheric emission.
The physical mechanism at the origin of gamma-ray bursts (GRBs) is far from being completely understood. Describing their emission up to very high energies (GeV-TeV) is one of the most challenging and important tasks needed to unveil the physics of these peculiar events.
Using data collected by the HAWC gamma-ray observatory, we search for TeV emission coming from a sample of GRBs detected by...
Many different physical processes have been suggested to explain the prompt gamma-ray emission in gamma-ray bursts (GRBs). Although there are examples of both bursts with photospheric and synchrotron emission origins, these distinct spectral appearances have not
been generalized to large samples of GRBs. Here, we search for signatures of the different emission mechanisms in the full {\it...
The Fermi GBM catalog contains general physical quantities of the observed objects and also estimated parameters (peak energy, spectral indices, intensity) from four fitted spectral models (Band, smoothly broken power law, Comptonized, power law) for the peak flux and the fluence. We studied the nature of the errors of the peak flux, the fluence, and duration parameters. We have found a linear...
The sky distribution of Gamma-Ray Bursts (GRBs) has been intensively studied for more than two decades. Most of these studies, test the isotropy of GRBs based on the sky number density distribution. We propose a new method which inspects the isotropy of the properties of GRBs such as their duration, fluences and peak fluxes at various energy bands and different time scales. The method was...
