The Prompt Gamma-Ray and Afterglow Energies of Short-Duration Gamma-Ray Bursts

Details The Prompt Gamma-Ray and Afterglow Energies of Short-Duration Gamma-Ray Bursts The Prompt Gamma-Ray and Afterglow Energies of Short-Duration Gamma-Ray Bursts

2007-02-27

arxiv.org/abs/astro-ph/0702694v1

Astronomy and Astrophysics

Astrophysics

Submitted to ApJ; 9 pages, 2 figures, 1 table

Scientific paper

10.1086/522195

I present an analysis of the gamma-ray and afterglow energies of the complete sample of 17 short duration GRBs with prompt X-ray follow-up. I find that 80% of the bursts exhibit a linear correlation between their gamma-ray fluence and the afterglow X-ray flux normalized to t=1 d, a proxy for the kinetic energy of the blast wave ($F_{X,1}~F_{gamma}^1.01). An even tighter correlation is evident between E_{gamma,iso} and L_{X,1} for the subset of 13 bursts with measured or constrained redshifts. The remaining 20% of the bursts have values of F_{X,1}/F_{gamma} that are suppressed by about three orders of magnitude, likely because of low circumburst densities (Nakar 2007). These results have several important implications: (i) The X-ray luminosity is generally a robust proxy for the blast wave kinetic energy, indicating nu_X>nu_c and hence a circumburst density n>0.05 cm^{-3}; (ii) most short GRBs have a narrow range of gamma-ray efficiency, with ~0.85 and a spread of 0.14 dex; and (iii) the isotropic-equivalent energies span 10^{48}-10^{52} erg. Furthermore, I find tentative evidence for jet collimation in the two bursts with the highest E_{gamma,iso}, perhaps indicative of the same inverse correlation that leads to a narrow distribution of true energies in long GRBs. I find no clear evidence for a relation between the overall energy release and host galaxy type, but a positive correlation with duration may be present, albeit with a large scatter. Finally, I note that the outlier fraction of 20% is similar to the proposed fraction of short GRBs from dynamically-formed neutron star binaries in globular clusters. This scenario may naturally explain the bimodality of the F_{X,1}/F_{gamma} distribution and the low circumburst densities without invoking speculative kick velocities of several hundred km/s.

Affiliated with

Also associated with

No associations

Rating

The Prompt Gamma-Ray and Afterglow Energies of Short-Duration Gamma-Ray Bursts does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The Prompt Gamma-Ray and Afterglow Energies of Short-Duration Gamma-Ray Bursts, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Prompt Gamma-Ray and Afterglow Energies of Short-Duration Gamma-Ray Bursts will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-205991