The Thermal Composition Of The Prompt Radiation Of Gamma-ray Bursts Is Studied Base On The Fermi Satellite Date

Gamma-ray burst(GRB)jet compositions are still one fundamental question.The thermal compositions are found in a few gamma-ray bursts only which are predicted by the fireball model.most spectra of GRB can be well fitted by a Band function.This work,we base on the Fermi satellite data to explore the properties of GRBs.Like,how much GRBs can be observed a prominent thermal component?how about the parameters?This work is based on the 517 bright GRBs which detected by Fermi satellite from 2008 to 2019,We systematically study the thermal component of the prompt radiation by those typical spectrum models and Bayesian Information Criterion(BIC).we conclude the summaries as follows:(1)There are 32 GRBs contain a prominent thermal component(occupy 6.2%).19 of them can be divide into gold sample,9 of them can be divide into sliver sample.The least 4 events are divided into copper sample.(2)Bases on the 32 great samples,we conclude the parameters like the temperature and the flux of the blackbody.We found a typical temperature kT of blackbody in the time integral spectrum and time resolved spectrum were log(kT/keV)=(1.36±0.16)and log(kT/keV)=(1.42±0.27),respectively.And,the typical ratio to the flux of blackbody and total observed flux were logfth=(-1.71±0.52)and logfth=(-1.46±0.45)in the time integral spectrum and time resolved spectrum,respectively.(3)Bases on the hybrid relativistic outflow photosphere model,work gives a deeper explore in 8 gold samples which redshift has been confirmed.At the center engine radii r0=107 cm,r0=108 cm and r0=109 cm.We got the center engine radii r0?107 cm,r0=108 cm and r0?109 cm.We got the typical values of:1)the magnetization of the central engine 1+?0 are 1,1 and log(1+?0)=1.2±0.4,respectively,the results show that the smaller r0 is,the smaller the value is 1+?;2)dimensionless entropy ? are log ?=3.2±1.8?log ?=2.4±1.6 and log ?=2.1±0.8,the results show that the smaller r0 is,the smaller the value is ?;3)the photosphere rph are log(rph/cm)=12.0±0.5?log(rph/cm)=11·9±0·5 and log(rph/cm)=11·8±0·5,respectively;4)the photosphere Lorentz factor rph are log ?ph=3.0±0·6?log?ph=3.1±0.8 and log?ph=2.4±0.5,respectively;5)the magnetization of the photosphere 1+?ph at r0?107 cm,r0?108 cm,the typical value is 1,but r0?109 cm,the distribution is roughly log(1+?ph)=1.2;6)most of the magnetization at distance 1015 cm from center engine 1+?15 are 1,with a maximum value of 6.5(4)Some of the correlation between parameters of thermal component also was concluded:kT-FBB relation?kT-? relation?kT-rph relation??ph rph relation and kT-?ph relation.During the search,it was found that GRB 130310A was very special.In the early period of the GRB 130310A,there were thermal components(kT? 6 keV),and a very high peak energy Ep about is 9265.0 keV.Ep evolution show hard-to-soft evolution.Ep-Liso diagram shows that the high peak energy Ep does not come from the photosphere model.Assuming the redshift is z=0.1?8,the calculation results of the magnetization parameter at?1015 cm(?15)are as follows,for r0?109 cm,1+?15>1,However,the value of 1+?15=1 in the z=3.The probability of its high Ep originating from ICMART is low.The photosphere-internal shock seems capable of interpreting the high peak energy,which requires the electron Lorentz factor ye?60 and ?e?0.06.