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

• Published in: Science China. Physics, mechanics & astronomy Vol. 53; no. Suppl 1; pp. 64 - 68
• Main Authors: Lin, Lin, Liang, EnWei, Zhang, ShuangNan
• Format: Journal Article
• Language: English
• Published: Heidelberg SP Science China Press 2010; Springer Nature B.V
• Subjects: Astronomy; Classical and Continuum Physics; Gamma ray bursts; Gamma rays; Hubble diagram; Massive stars; Observations and Techniques; Physics; Physics and Astronomy; Red shift; Research Papers; high energy phenomenon; gamma-ray bursts; cosmology
• DOI: 10.1007/s11433-010-0027-z
• ISSN: 1674-7348

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 T 90 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 T 90 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 E p =(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.