School of Astroparticle Physics
May 27th - June 1st, 2013
OHP, Saint Michel l'Observatoire

Gravitational Waves

Gamma-ray Bursts

Frédéric DAIGNE
Institut d'Astrophysique de Paris (IAP)

Course
This lecture on gamma-ray burst will summarize the main observational facts and the corresponding constraints on the models. The general physical scenario will be described, as well as the main open issues. A focus will be given to the identification of gamma-ray burst progenitors and the consequences for the emission of gravitational waves.
Chapters
  1. Observational facts
    1. Prompt emission
    2. Afterglow emission
  2. Main constraints on GRB models
  3. A three step scenario
    1. Initial event, central engine, relativistic ejection
    2. Internal dissipation in the relativistic outflow and prompt emission
    3. Deceleration by the external medium and afterglow emission
    4. Open issues
  4. Gamma-ray bursts as sources of gravitational waves
  5. Identification of GRB progenitors
  6. Consequences for the emisison of gravitational waves


Abstract

Gamma-ray bursts are probably the most extreme cases of explosive phenomena associated to the end of stellar evolution. Their huge radiated power allows to detect them at cosmological distance. The observed emission during a gamma-ray burst is produced by an ultra-relativistic outflow ejected by a new born compact source. The first "prompt" phase of emission, characterized by a short duration, a high variability and a gamma-ray dominated spectrum, is due to a dissipative mechanism within the jet itself. The second "afterglow" phase is associated to the deceleration of the jet by the external medium : the flux is rapidly decreasing, as well as the characteristic frequency which goes from X-rays to the visible and radio domains. Gamma-ray bursts can be separated in two classes according to their duration. These two classes seem to differ mainly by the nature of the initial event responsible for the formation of the central compact object. Long gamma-ray bursts are associated to the gravitational collapse of some very massive  stars. The status of short gamma-ray bursts is less clear. The most discussed scenario is the merger of a binary system of two neutron stars or a neutron star and a black hole. For this reason, short gamma-ray bursts appear as promising sources of gravitational waves.
Bibliography
    • Hughes, "Gravitational Waves from Merging Compact Binaries", Annual Review of Astronomy & Astrophysics, 47,  107 (2009)
    • Nakar, E., "Short hard gamma-ray bursts", Physics Reports, 442, 166 (2007)
    • Kouveliotou et al., "Gamma-ray bursts", Cambridge University Press, 2013
    • G. Vedrenne & J.L. Atteia, "Gamma-ray bursts, the brightest explosions in the Universe", Springer 2009
    • T. Piran, "The physics of gamma-ray bursts", Rev. Mod. Phys. 76 (2004) 1143

 

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