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High-Energy Gamma-Ray Afterglows from Low-Luminosity Gamma-Ray Burst

High-Energy Gamma-Ray Afterglows from Low-Luminosity Gamma-Ray Burst. Hao-Ning He 1 , Xiang-Yu Wang 1 , Yun-Wei Yu 1,2 and Peter M é sz á ros 3,4 1 Department of Astronomy, Nanjing University, Nanjing 210093, China 2 Institute of Astrophysics, Huazhong Normal University, Wuhan 430079, China

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High-Energy Gamma-Ray Afterglows from Low-Luminosity Gamma-Ray Burst

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  1. High-Energy Gamma-Ray Afterglows from Low-Luminosity Gamma-Ray Burst • Hao-Ning He1, Xiang-Yu Wang1, Yun-Wei Yu1,2 and Peter Mészáros3,4 • 1 Department of Astronomy, Nanjing University, Nanjing 210093, China • 2 Institute of Astrophysics, Huazhong Normal University, Wuhan 430079, China • 3 Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA • 4 Department of Physics, Pennsylvania State University, Univer-sity Park, PA 16802, USA

  2. Outline • Models • Spectra • Light curves • Detectability by Fermi LAT • Conclusion

  3. Three low-luminosity supernova-GRBs • low luminosity • smooth light curves • spectra: simple power-law with a high energy cutoff

  4. Two scenarios of low-luminosity GRBs • We consider a spherical GRB ejecta carrying a total energy of E expanding into a surrounding wind medium with density profile , where with • Conventional relativistic model: ejecta with Lorentz factor ~10 (e.g. Mazzali 2006; Fan et al. 2006; Toma et al. 2006). • Trans-relativistic model: ejecta with Lorentz factor ~2 (Waxman 2004; Waxman, Mészáros & Campana,2007;Wang, Li, Waxman & Mészáros 2007; Ando & Mészáros, 2008). supernova observer wind medium external shock

  5. Seed photons from supernova syn SSC SNIC seed photons supernova observer wind medium external shock • Late-time SN emission, powered by radioactive decay, which peaks at ten days • Early thermal UV-optical emission from cooling SN envelope after being heated by the radiation-dominated shock (Waxman et al. 2007; Soderberg et al. 2008; Chevalier & Fransson 2008)

  6. Spectra • full Klein-Nishina cross section for IC • the opacity for photon annihilation • different dominant components • differrent flux levels We consider: p=2.2 We get:

  7. Light curves • different figurations • different flux levels • different dominant components light curves at 1GeV p=2.2

  8. Detectability of Fermi We take the fluence threshold of Fermi LAT as: (Zhang & Mészáros 2001b, Gou & Mészáros 2007 and Yu, Liu & Dai 2007)

  9. double total energy SN1998bw-like hypernovae: (Woosley et al.1999)

  10. Conclusion • High-energy gamma-ray emission can be detected in both models as long as is large enough, although a detection from the conventional relativistic ejecta is much easier. • With future high energy gamma-ray observations by Fermi LAT, one can expect to be able to distinguish between the two models through different observational features and constraint parameters of the model. different light curve shapes different flux levels different dominant components different dynamical evolutions different observational features different initial Lorentz factors

  11. Thank you! 谢谢!

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