GRB 090423:Marking the death of a massive star at z=8.2  

作　　者：LIN Lin1,LIANG EnWei2 & ZHANG ShuangNan3 1 Department of Physics and Center for Astrophysics,Tsinghua University,Beijing 100084,China 2 Department of Physics,Guangxi University,Nanning 530004,China 3 Key Laboratory of Particle Astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China 

出　　处：《Science China(Physics,Mechanics & Astronomy)》2010年第S1期64-68,共5页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 10821061, 10733010, 10725313, and 10873002);the National Basic Research Program of China (Grant No. 2009CB824800);Guangxi SHI-BAI-QIAN Project (Grant No. 2007201);the Program for 100 Young and Middle-aged Disciplinary Leaders in Guangxi Higher Education Institutions, the Research Foundation of Guangxi University (Grant No. M30520);the Ministry of Education of China, Directional Research Project of the Academy of Sciences (Grant No. KJCX2-YW-T03)

摘　　要：GRB 090423 is the new high-z record holder of Gamma-ray bursts(GRBs) with z-8.2.We present a detailed analysis of both the spectral and temporal features of GRB 090423 observed with Swift/BAT and Fermi/GBM.We find that the T90 observed with BAT in the 15-150 keV band is 13.2 s,corresponding to-1.4 s at z=8.2.It once again gives rise to the issue of whether the progenitors of high-z GRBs are massive stars or mergers since the discovery of GRB 080913 at z=6.7.In comparison with the T90 distribution in the burst frame of the current redshift-known GRB sample,we find that it is marginally grouped into the long group(Type II GRBs).The spectrum observed with both BAT and GBM is well fitted by a power-law with exponential cutoff,which yields an Ep=(50.4±7.0) keV.The event satisfies the Amati-relation well for Type II GRBs within their 3σ uncertainty range.Our results indicate that this event would be produced by the death of a massive star.Based on the Amati-relation,we derive its distance modulus,which follows the Hubble diagram of the concordance cosmology model at a redshift of-8.2.GRB 090423 is the new high-z record holder of Gamma-ray bursts(GRBs) with z-8.2.We present a detailed analysis of both the spectral and temporal features of GRB 090423 observed with Swift/BAT and Fermi/GBM.We find that the T90 observed with BAT in the 15-150 keV band is 13.2 s,corresponding to-1.4 s at z=8.2.It once again gives rise to the issue of whether the progenitors of high-z GRBs are massive stars or mergers since the discovery of GRB 080913 at z=6.7.In comparison with the T90 distribution in the burst frame of the current redshift-known GRB sample,we find that it is marginally grouped into the long group(Type II GRBs).The spectrum observed with both BAT and GBM is well fitted by a power-law with exponential cutoff,which yields an Ep=(50.4±7.0) keV.The event satisfies the Amati-relation well for Type II GRBs within their 3σ uncertainty range.Our results indicate that this event would be produced by the death of a massive star.Based on the Amati-relation,we derive its distance modulus,which follows the Hubble diagram of the concordance cosmology model at a redshift of-8.2.

关 键 词：GAMMA-RAY BURSTS high energy phenomenon COSMOLOGY 

分 类 号：P172.3[天文地球—天文学]