15,222 research outputs found
Highlights of the Rome Workshop on Gamma-Ray Bursts in the Afterglow Era
I review some of the highlights of the Rome Workshop on Gamma-Ray Bursts, and
discuss some of the questions these results pose about the nature and origin of
gamma-ray bursts.Comment: 8 pages, Proceedings of Gamma-Ray Bursts in the Afterglow Era, Nov.
1998, Rome, F. Frontera & L. Piro eds., A&A Suppl. Ser., in pres
Issues in the analysis and interpretation of cyclotron lines in gamma ray bursts
The Bayesian approach is discussed to establishing the existence of lines, the importance of observing multiple cyclotron harmonics in determining physical parameters from the lines, and evidence from cyclotron lines of neutron star rotation
Continuum and line spectra of degenerate dwarf X-ray sources
Recent observations of X-ray sources are summarized. Unresolved issues concerning these sources are discussed and an outline of the kinds of X-ray observations that would best advance the understanding of these sources is presented
GeV Gamma-Ray Sources
We report on the preliminary extension of our work on cataloging the GeV sky to approximately 7 years of CGRO/EGRET observations with special emphasis on a search for transient sources. The search method and significance levels are presented. Our initial results on 13 possible transients indicate that 3 may be new gamma-ray sources. Sixteen new steady GeV sources are also detected, 3 of which have never been reported as gamma-ray sources
Gamma-Ray Burst Jet Profiles And Their Signatures
HETE-II and BeppoSAX have produced a sample of GRBs and XRFs with known
redshifts and . This sample provides four important empirical
constraints on the nature of the source jets: Log is approximately
uniformly distributed over several orders of magnitude; the inferred prompt
energy Log is narrowly distributed; the Amati relation holds
between and ; and the Ghirlanda relation holds between
and .
We explore the implications of these constraints for GRB jet structure during
the prompt emission phase. We infer the underlying angular profiles from the
first two of the above constraints assuming all jets have the same profile and
total energy, and show that such ``universal jet'' models cannot satisfy both
constraints.
We introduce a general and efficient method for calculating relativistic
emission distributions and distributions from jets with arbitrary
(smooth) angular jet profiles. We also exhibit explicit analytical formulas for
emission from top-hat jets (which are not smooth). We use these methods to
exhibit and as a function of viewing angle, for several
interesting families of GRB jet profiles. We use the same methods to calculate
expected frequency distributions of and for the same
families of models.
We then proceed to explore the behavior of universal jet models under a range
of profile shapes and parameters, to map the extent to which these models can
conform to the above four empirical constraints.Comment: 71 page, 33 figures. Submitted to Ap
- …