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

Progenitor of GRB  Long GRB (T 90 >2s) Type II (Long soft GRB?) collapse of massive stars (e.g. Wolf ‐ Rayet star) galaxy disk (“high”/moderate density ambient medium)  Short GRB (T 90 <2s) Type I GRB (Short hard GRB?) mergers (NS ‐ NS, BH ‐ NS) galaxy halo (low density ambient medium)  The circumburst environment can shed some light on GRB’s origin

GRB afterglow  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

Kumar&Barniol ‐ Duran 2009a GRB 080916C Cenko et al. 2011 A two component jet model for GRB 090902B (Liu & Wang 2011) Kumar&Barniol ‐ Duran 2009b

Multiband radiation of GRB afterglow  High Energy (>100MeV) ,X ‐ ray, Optical, Radio Universal synchrotron spectrum from forward shock X ‐ ray 10keV Radio Gamma ray Optical >100MeV Radio      , ' a m c c

synchrotron spectrum X ‐ ray (p=2.2) 10keV Radio Gamma ray Optical >100MeV Radio    ,   ' a m c c with (Liu et al. 2013)

Synchrotron Self ‐ Compton component in High energy Afterglow (Dermer et al 2000, Zhang & Meszaros 2001, Zou et al. 2009, Wang et al. 2013, Fan et al .2013 and etc) Emax of synchrotron radiation is limited Synchrotron radiation can hardly produce >10 GeV (constrained by synchrotron cooling) photons after a few hundred seconds Synchrotron radiation can hardly produce >100 MeV photons after ~1000s (In the decaying micro ‐ turbulence magnetic field scenario) See Prof. Wang talk

Lightcurve of extended high energy emission     (2 3 )/4 1.15 p Syn component F T T (p=2.2) in both ISM case and wind case  If E max ‐ > E ob , an exponential ‐ like cutoff will occur     (11 9 )/8 p 1.1 (p=2.2) in ISM case F T T  SSC component     2.2 p F T T (p=2.2) in wind case 

(In the decaying micro ‐ turbulence magnetic field scenario) Wang, Liu & Lemoine 2013

(In the decaying micro ‐ turbulence magnetic field scenario) Wang, Liu & Lemoine 2013

Synchrotron cooling ‐ constrained E max GRB 130427A Liu, Wang & Wu 2013

Conclusion  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. Thanks for you attention