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.
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
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)
