An Investigation Of The X-ray Flares Of X-ray Flashes That Are Subclass-gamma-ray Bursts

Gamma-ray burst(briefly called GRB)is the most violent burst,which has a large gamma-ray emission during short time.In Galactic coordinate,the distribution of GRBs are isotropic.But the radial distribution of GRBs are inhomogeneous.Durations of GRBs range from milliseconds to thousands of seconds,while durations of long bursts are greater than 2 seconds and durations of short bursts are less than 2 seconds.For short bursts,the typical durations are 0.3 seconds.For long bursts,the typical durations are 30 seconds.The pulse of GRB is asymmetric and rise time is less than decay time.The spectrum of GRBs can be discribed by Band function which consists of three parameters:low energy index(typical value:-1)?high energy index(typical value:-2.2)and peak energy(typical value:250 keV).The GRBs are classified into three types:X-ray flash(briefly called XRF)?X-ray rich GRB(briefly called XRR)and classical GRB(briefly called C-GRB)based on the energy band in which the GRB has a large emission.In GRB s,the peak time in low energy band is later than the peak time in high energy band,and the pulse keeps self-similar both in low and high energy band Some GRBs have thermal emission in spectrum.The redshift distribution is different between short bursts and long bursts.And the spectrum of short burst is harder than the one of long burstXRF is a GRB which has a large emission in X-ray energy band.XRF is define as log[SX(25-50keV)/S?(50-100keV)]>1.32.The T90 is similar among XRFs·XRRs and C-GRB s,but peak energy distribution is different among XRFs>XRRs and C-GRBs.For GRB 011121 and XRF 020903,their afterglows have a rebright which is caused by SNe.The XRF and low-luminous GRB have a similar luminosity and typical value is 1047 erg·s-1but XRF has different z-t obs?relationship from subluminous-long GRBX-ray flares are short flare in X-ray afterglows of GRB s.The pulses of X-ray flares are similar to the pulses of GRB s.The durations of X-ray flares range from hundreds of seconds to thousands of seconds.In the fraction of GRBs,the flux of X-ray flare reaches to the flux of prompt emission.The spectrum of X-ray flare is harder than the spectrum of X-ray afterglow.In X-ray flare,the spectrum evolves from hardness to softness.In X-ray flare the peak time in low energy band is later than the peak time in high energy band.The spectrum of early X-ray flares is harder than the one of late X-ray flares,but there is a similar w-tp relationship between the early X-ray flare and the late X-ray flare.In some of X-ray flares,there is thermal emission in spectrum.The optical rebright is related to X-ray flare,because there is a similar w-tp relationship between the optical rebright and X-ray flare.The X-ray flares of short bursts are dimmer than X-ray flares of long bursts.For short bursts,their X-ray flares reside both in early-type galaxies and late-type galaxies.The spectrum of X-ray flare evolves from hardness to softness both in short bursts and long bursts,while X-ray flares have a similar w-tp relationship both in short bursts and long bursts.We take a invetigation of properties of X-ray flares among XRFs>XRRs and C-GRBs.XRFs?XRRs and C-GRB s can be obtained from Swift-BAT observation during time from December 17,2004 to December 2,2016.X-ray flares are obtained from Chincarini et al.(2010)and Yi et al.(2016),respectively.For Chincarini et al.(2018),X-ray flares are observed between April,2005 and March,2008.For Yi et al.(2018),X-ray flares are observed between April,2005 and March,2015.In GRBs with X-ray flare,we examine the T90 distribution among XRFs?XRRs and C-GRBs.And we show the XRF?XRR and C-GRB distribution in the plane S(25-50keV)/S(50-100keV)-T90.Applying the power-law and cutoff power-law to fit the spectrum of XRFs?XRRs and C-GRBs,we show the spectral index ?PL and ?CPL distribution and we also show the spectral index of XRFs?XRRs and C-GRBs with X-ray flares.We examine the ratio of X-ray flare fluence to prompt emission fluence among XRFs?XRRs and C-GRBs.We examine the duration distribution and the peak time distribution of X-ray flare among XRFs?XRRs and C-GRB s.We examine the correlation between the duration and the peak time of X-ray flare among XRFs?XRRs and C-GRBs.We examine the X-ray flare distribution in plane ?F/F-w/tp among XRFs?XRRs and C-GRBs.We further examine the distribution of properties of spectra of X-ray flare and show the distribution of spectral parameters of X-ray flares among XRF?XRR and C-GRB.We find that the ratio of X-ray flare fluence to prompt emission fluence distribution is different between XRFs and C-GRBs.We find that the correlation between the duration and the peak time of X-ray flare is different between XRFs and C-GRB s.There are different spectral index distribution between XRF and C-GRB,however,we do not find the difference of spectral index distribution of X-ray flares among XRFs?XRRs and C-GRBs.And the typical value of spectral index of X-ray flare is close to the one of XRFs.XRFs include more number of bright X-ray flares than C-GRBs.X-ray flares may be related to XRFs.Some of GRB s with bright X-ray flares may be inclined to XRFs.