Nava 2010 Fermi GBM 438个暴的谱分析

主要内容:
发现80%的暴是在高能段指数下降，而不是Band谱。其他细节内容在摘要里。

精彩摘抄:

红色是短暴的，蓝色是长暴的

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Title:		Spectral properties of 438 GRBs detected by Fermi/GBM
Authors:		Nava, L.; Ghirlanda, G.; Ghisellini, G.; Celotti, A.
Publication:		eprint arXiv:1012.2863
Publication Date:		12/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		Accepted for publication in A&A
Bibliographic Code:		2010arXiv1012.2863N

Abstract

We present the results of the spectral analysis of the public data of 438 Gamma Ray Bursts (GRBs) detected by the Fermi Gamma ray Burst Monitor (GBM) up to March 2010. For 432 bursts we could fit the time integrated spectrum. In 318 cases we can reliably constrain the peak energy Epeak of their \nu F_\nu spectrum by analyzing their time integrated spectrum between 8 keV and 35 MeV. 80% of these spectra are fitted by a power law with an exponential cutoff, and the remaining with the Band function. Among these 318 GRBs, 274 and 44 belong to the long and short GRB class, respectively. Long GRBs have a typical peak energy Epeak=160 keV and low energy spectral index alpha=-0.92. Short GRBs have harder peak energy (Epeak=490 keV) and harder low energy spectral index (alpha=-0.50) than long bursts. For each Fermi GRB we analyzed also the spectrum corresponding to the peak flux of the burst. On average, the peak spectrum has harder low energy spectral index but similar Epeak than the corresponding time-integrated spectrum for the same burst. The spectral parameters derived in our analysis of Fermi/GBM bursts are globally consistent with those reported in the GRB Cicular Network (GCN) archive after December 2008, while we found systematic differences, concerning the low energy power law index, for earlier bursts.

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· arXiv e-print (arXiv:1012.3968)

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Title:		Fermi/GBM and BATSE Gamma-Ray Bursts: comparison of the spectral properties
Authors:		Nava, Lara; Ghirlanda, Giancarlo; Ghisellini, Gabriele; Celotti, Annalisa
Publication:		eprint arXiv:1012.3968
Publication Date:		12/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		The subject of this work is similar to our paper arXiv:1004.1410, that was rejected because based on Fermi/GBM spectral preliminary results reported in GCN Circulars. The present work is based on our own analysis of Fermi/GBM bursts detected up to March 2010 (presented in arXiv:1012.2863). Submitted to A&A
Bibliographic Code:		2010arXiv1012.3968N

Abstract

The Gamma-ray Burst Monitor (GBM) on board Fermi allows to study the spectra of Gamma Ray Bursts (GRBs) over an unprecedented wide energy range (8 keV - 35 MeV). We compare the spectral properties of short and long GRBs detected by the GBM (up to March 2010) with those of GRBs detected by the BATSE instrument on board the CGRO. GBM and BATSE long bursts have similar distributions of fluence (F), Epeak and peak flux (P) but GBM bursts have a slightly harder low-energy spectral index \alpha with respect to BATSE GRBs. GBM and BATSE short bursts have similar distributions of fluence, \alpha and peak flux, with GBM bursts having slightly larger Epeak. We discuss these properties in light of the found correlations between Epeak and the fluence and the peak flux. GBM bursts confirm that these correlations are not determined by instrumental selection effects. Indeed, GBM bursts extend the Epeak-Fluence and Epeak-P correlations both in fluence/peak flux and in peak energy. No GBM long burst with Epeak exceeding a few MeV is found, despite the possibility of detecting it. Similarly to what found with BATSE, there are 3% of GBM long bursts (and almost all short ones) that are outliers at more than 3\sigma of the Epeak-Eiso correlation. Instead there is no outlier of the Epeak-Lp,iso correlation, for both long and short GBM bursts.

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