GRB 090510: Early LAT emission is not from external shock

Hao Ning He, Xue Feng Wu, Kenji Toma, Peter Mészáros, Xiang Yu Wang

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Long-lived high-energy (> 100MeV) emission, a common feature of most Fermi-LAT detected gamma-ray burst, is detected up to ∼ 102 s in the short GRB 090510. We study the origin of this long-lived high-energy emission, using broad-band observations including X-ray and optical data. We confirm that the late > 100 MeV, X-ray and optical emission can be naturally explained via synchrotron emission from an adiabatic forward shock propagating into a homogeneous ambient medium with low number density under significant Klein-Nishina effects. Under the constraints from the low-energy observations, the adiabatic forward shock synchrotron emission is consistent with the later-time (t > 2s) high-energy emission, but falls below the early-time (t < 2s) high energy emission. Thus we argue that an extra high energy component is needed at early times. A standard reverse shock origin is found to be inconsistent with this extra component. Therefore, we attribute the early part of the high-energy emission (t < 2s) to the prompt component, and the long-lived high energy emission (t > 2s) to the adiabatic forward shock synchrotron afterglow radiation. This avoids the requirement for an extremely high initial Lorentz factor.

Original languageEnglish
Title of host publicationGamma Ray Bursts 2010, GRB 2010
Number of pages4
Publication statusPublished - 2011 Sep 12
Externally publishedYes
EventGamma Ray Bursts 2010, GRB 2010 - Annapolis, MD, United States
Duration: 2010 Nov 12010 Nov 4

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


ConferenceGamma Ray Bursts 2010, GRB 2010
Country/TerritoryUnited States
CityAnnapolis, MD


  • Burst
  • Gamma-rays
  • Non-thermal
  • Radiation mechanism

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Plant Science
  • Physics and Astronomy(all)
  • Nature and Landscape Conservation


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