On GRB's Extended LAT Emission and its Implication for the - - PowerPoint PPT Presentation

On GRB's Extended LAT Emission and its Implication for the Circumburst Environment

Ruo‐Yu Liu Collaborator: Xiang‐Yu Wang, Xue‐Feng Wu, Martin Lemoine

FAN4 HongKong 8.Jul.2013 Nanjing University Max‐Planck‐Institute for Nuclear physics

 Long GRB (T90>2s) collapse of massive stars (e.g. Wolf‐Rayet star) galaxy disk (“high”/moderate density ambient medium)  Short GRB (T90<2s) mergers (NS‐NS, BH‐NS) galaxy halo (low density ambient medium)

 The circumburst environment can shed some light

• n GRB’s origin

Progenitor of GRB

Type II (Long soft GRB?) Type I GRB (Short hard GRB?)

 Fireball model of Afterglow

(Meszaros&Rees 1994 ,Sari&Piran 1995, Sari et al. 1998, Dai&Lu 1998)

 , , , , ,

,

 Modeling multiband afterglow can give some information of circumburst environment

GRB afterglow

Cenko et al. 2011 Kumar&Barniol‐Duran 2009a A two component jet model for GRB 090902B (Liu & Wang 2011) Kumar&Barniol‐Duran 2009b

GRB 080916C

 High Energy (>100MeV) ,X‐ray, Optical, Radio

Multiband radiation of GRB afterglow

a



m

 ' 

c



,

c



Gamma ray

>100MeV X‐ray 10keV Optical Radio Radio

Universal synchrotron spectrum from forward shock

a



m

 ' 

c



,

c



Gamma ray

>100MeV X‐ray 10keV Optical Radio Radio

synchrotron spectrum with

(Liu et al. 2013)

(p=2.2)

Synchrotron Self‐Compton component in High energy Afterglow

Emax of synchrotron radiation is limited (constrained by synchrotron cooling) (In the decaying micro‐turbulence magnetic field scenario)

(Dermer et al 2000, Zhang & Meszaros 2001, Zou et al. 2009, Wang et al. 2013, Fan et al .2013 and etc)

Synchrotron radiation can hardly produce >10 GeV photons after a few hundred seconds Synchrotron radiation can hardly produce >100 MeV photons after ~1000s See Prof. Wang talk

Lightcurve of extended high energy emission

(p=2.2) in both ISM case and wind case Syn component

(2 3 )/4 1.15 p

F T T

  

 

SSC component

(11 9 )/8 1.1 p

F T T

  

 

(p=2.2) in ISM case

2.2 p

F T T

  

 

(p=2.2) in wind case If Emax ‐> Eob , an exponential‐like cutoff will occur

Wang, Liu & Lemoine 2013

(In the decaying micro‐turbulence magnetic field scenario)

(In the decaying micro‐turbulence magnetic field scenario)

Wang, Liu & Lemoine 2013

Liu, Wang & Wu 2013

Synchrotron cooling‐ constrained Emax

GRB 130427A

 Considering the KN effect in X‐ray afterglow modeling enhances the obtained circumburst density  The enhanced circumburst density potentially promises a SSC component from forward shock  The extended high energy emissions (especially the >10 GeV photons) likely have a SSC origin  Whether the SSC component shows up, and (if present) its temporal behavior can help us diagnose the circumburst

• environment. The presence of a SSC component in LAT‐

detected GRB implies the density of circumburst environment is not low as indicated in previous studies.

Conclusion

Thanks for you attention