| GRB 130310A: very high peak energy and thermal emission |
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| 作者姓名： | Song-Mei Qin Lu-Yao Jiang Xiang-Gao Wang |
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| 作者单位： | Mathematics and Physics Section;Guangxi Key Laboratory for Relativistic Astrophysics;GXU-NAOC Center for Astrophysics and Space Sciences |
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| 基金项目： | supported by the National Natural Science Foundation of China(Grant Nos.11673006,U1938201,11533003);the Guangxi Science Foundation(Grant Nos.2016GXNSFFA380006,2017GXNSFBA198206,2017AD22006,2018GXNSFGA281007);the OneHundred-Talents Program of Guangxi colleges;High level innovation team and outstanding scholar program in Guangxi colleges。 |
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| 摘 要： | The special GRB 130310 A was observed by Fermi Gamma-Ray Burst Monitor and Large Area Telescope,with T90~2.4 s.With a combination of a Band function and a blackbody(BB)function,the time-resolved spectral analysis of GRB 130310 A confirmed that there is a sub-dominate thermal component in the early period(e.g.,slice T0+4.03-4.14]s)spectrum with BB temperature(kT)being~7~5 keV,which can be interpreted as photosphere emission.The precursor of GRB 130310 A can be fitted well with a BB component with kT~45 keV,which is higher than that of the main burst.It suggests that the radiation of GRB 130310 A is in transition from thermal to non-thermal.Such a transition is an indication of the change in jet composition from a fireball to a Poynting-flux-dominated jet.A very high peak energy is obtained in the first time bin,with the peak energy Ep of the Band component for Band+BB and Band model being~8.5~5.2 MeV and~11.1~7.4 MeV,respectively.Afterwards,the Ep drops to~1 MeV.The Ep evolution patterns with respect to the pulses in the GRB 130310 A light curves show a hard-to-soft evolution.The interpretation of the high peak energy Ep within the photosphere and internal shock model is difficult.It also suggests that at least for some bursts,the Band component must invoke a non-thermal origin in the optically thin region of a GRB outflow.Assuming the redshift is z~0.1~8,the radius of the jet base r0~109 cm to allow(1+σ15)>1 in line with the calculation results of the magnetization parameter at~1015 cm(σ15).However,the value of(1+σ15)is■1 in the zone z around 3 for r0~109 cm,suggesting the non-excluded possibility that the origin is from ICMART with a low value.The photosphere-internal shock seems capable of interpreting the high peak energy,which requires electron Lorentz factorγe~60 andεe~0.06.
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| 关 键 词： | gamma rays bursts general-gamma-ray burst individual(GRB 130310A)-radiation mechanisms thermal-radiation mechanisms NON-THERMAL |
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