Spectral properties of Fermi/GBM gamma-ray bursts and the GeV emission detection rate with Fermi/LAT  

作　　者：LV HouJun,LIANG EnWei & TONG XiaoFeng Department of Physics,Guangxi University,Nanning 530004,China 

出　　处：《Science China(Physics,Mechanics & Astronomy)》2010年第S1期73-77,共5页中国科学：物理学、力学、天文学（英文版）

基　　金：support by the National Basic Research Program of China (Grant No. 2009CB824800);the National Natural Science Foundation of China (Grant No. 10873002);Guangxi SHI-BAI-QIAN Project (Grant No. 2007201);the Program for 100 Young and Middle-aged Disciplinary Leaders in Guangxi Higher Education Instituions,and the Research Foundation of Guangxi University (Grant No. M30520)

摘　　要：With a sample of 58 Fermi/GBM GRBs detected before 2009 May,we compare the spectral properties of GBM GRBs with those detected by CGRO/BTASE and HETE-2.Our results show that the spectral index distributions are very consistent with those observed by BATSE.However,the Ep distribution is quite different from that observed with BATSE and HETE-2.The GBM GRBs tend to be softer than the BATSE sample,but harder than the HETE-2 sample.This may be due to the instrumental selection effects and artificial sample effect on the BATSE sample.The distribution of the pseudo redshifts derived from the luminosity indicator based on the Amati-relation shows rough consistency with the spectroscopic redshifts of Swift GRBs.We estimate the detection rate of GBM GRBs with LAT based on the observed spectrum in the GBM band,and the inferred burst ratio of LAT detection with over 5 photons to GBM detection is 6%,yielding a detection rate pf 12 GRBs/yr with over 5 photons in the 1-300 GeV band.This is roughly consistent with the results in the first half year of Fermi operation.The low detection rate compared with theoretical predictions is a key for revealing the radiation mechanisms and particle acceleration of the prompt gamma-rays.With a sample of 58 Fermi/GBM GRBs detected before 2009 May,we compare the spectral properties of GBM GRBs with those detected by CGRO/BTASE and HETE-2.Our results show that the spectral index distributions are very consistent with those observed by BATSE.However,the Ep distribution is quite different from that observed with BATSE and HETE-2.The GBM GRBs tend to be softer than the BATSE sample,but harder than the HETE-2 sample.This may be due to the instrumental selection effects and artificial sample effect on the BATSE sample.The distribution of the pseudo redshifts derived from the luminosity indicator based on the Amati-relation shows rough consistency with the spectroscopic redshifts of Swift GRBs.We estimate the detection rate of GBM GRBs with LAT based on the observed spectrum in the GBM band,and the inferred burst ratio of LAT detection with over 5 photons to GBM detection is 6%,yielding a detection rate pf 12 GRBs/yr with over 5 photons in the 1-300 GeV band.This is roughly consistent with the results in the first half year of Fermi operation.The low detection rate compared with theoretical predictions is a key for revealing the radiation mechanisms and particle acceleration of the prompt gamma-rays.

关 键 词：gamma-ray BURSTS high energy phenomenon spectrum statistics 

分 类 号：P172.3[天文地球—天文学]