Gamma-Ray Bursts

FIGURE 11 Time profiles for a sample of gamma-ray bursts (GRBs), obtained with the BATSE instrument aboard the Compton Gamma Ray Observatory. These profiles illustrate the rich diversity in temporal structure, intensities, and durations for gamma-ray bursts, no two of which are exactly alike in all respects. (Courtesy NASA and the CGRO BATSE Instrument Team.) 

For many years the mystery of the origin of gamma-ray bursts was compounded due to their lack of detection in any frequency band below the hard X-rays, a fact 

A fundamental question is the nature of the energetic event that sparks the detonation of the fireball itself. The enormous energies ( 10 ergs) implied by the cosmological distances inferred from the most recent observations of GRBs greatly restricts the number of possibilities. Only the mergers of the components of evolved binary systems 

Virtually all models for the ultimate energy source of GRBs involve an endpoint of stellar evolution, particularly of the most massive stars. Thus it has been proposed that the burst rate must be proportional to the overall cosmic star formation rate. This view is supported by the fact that the typical redshifts (z 1) associated with GRB host galaxies correspond to an epoch of early active star formation in the Universe. Burst counterparts also tend to be 

---

E. Costa, F. Frontera, J. Hjorth (Eds.), Gamma-Ray Bursts in the Afterglow Era... 

Berezhiani, Z., Bombaci, I., Drago, A., Frontera, F., Lavagno, A. (2003). Gamma Ray Bursts from delayed collapse of neutron stars to quark matter stars. Astrophys.J., 586 1250-1253. 

A color superconducting phase is a reasonable candidate for the state of strongly interacting matter for very large quark chemical potential [16-20], Many properties of such a state have been investigated for two and three flavor QCD. In some cases these results rely heavily on perturbation theory, which is applicable for very large chemical potentials. Some initial applications to supemovae explosions and gamma ray bursts can be found in [21] and [22] respectively, see also [27], The interested reader can find a discussion of the effects of color superconductivity on the mass-radius relationship of compact stars in [45]... 

Abstract Gamma-ray bursts are the most luminous and probably the most relativistic events in the universe. The last few years have seen a tremendous increase in our knowledge of these events, but the source of the bursts still remains elusive. I will summarize recent progress in this field with special emphasis on our understanding of the possible progenitor systems. 

Keywords gamma rays bursts supernovae stars neutron radiation processes non-thermal ... 

Like some other spectacular discoveries such as the cosmic microwave background, gamma-ray bursts (GRBs) were discovered by accident. Meant to monitor the outer space treaty , the American VELA satellites detected in July 1967 an intense flash of gamma-rays of unknown origin. It took until 1973 before the first detected GRBs were published for the scientific community (Klebesadel et al. 1973). 

The above listed observational facts impose constraints on the progenitor system(s) responsible for gamma-ray bursts. 

Keywords Gamma rays Gamma Ray Burst. Stars Neutron Stars, Strange Stars. Dense... 

This article reviews the current understanding of the supernova explosions. After a brief historical introduction the two main classes of supemovae are described starting from the classification scheme currently employed. The different energy inputs for supemovae are presented. Despite their rather different energy sources supernovae from different types reach very similar luminosities. A notable exception to this are the Gamma-Ray Bursts, which are several orders of magnitude more energetic. The characteristics of each supernova type are presented. 

---