PROMPT X-RAY AND OPTICAL EXCESS EMISSION DUE TO HADRONIC CASCADES IN GAMMA-RAY BURSTS

Journal Article · Mon Dec 20 00:00:00 EST 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/725/2/L121· OSTI ID:21454900

Asano, Katsuaki ^[1]; Inoue, Susumu ^[2]; Meszaros, Peter ^[3]

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1. Interactive Research Center of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)
2. Department of Physics, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502 (Japan)
3. Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)

A fraction of gamma-ray bursts (GRBs) exhibit distinct spectral features in their prompt emission below few tens of keV that exceed simple extrapolations of the low-energy power-law portion of the Band spectral model. This is also true for the prompt optical emission observed in several bursts. Through Monte Carlo simulations, we model such low-energy spectral excess components as hadronic cascade emission initiated by photomeson interactions of ultra-high-energy protons accelerated within GRB outflows. Synchrotron radiation from the cascading, secondary electron-positron pairs can naturally reproduce the observed soft spectra in the X-ray band, and in some cases the optical spectra as well. These components can be directly related to the higher energy radiation at GeV energies due to the hadronic cascades. Depending on the spectral shape, the total energy in protons is required to be comparable to or appreciably larger than the observed total photon energy. In particular, we apply our model to the excess X-ray and GeV emission of GRB 090902B, and the bright optical emission of the 'naked-eye' GRB 080319B. Besides the hard GeV components detected by Fermi, such X-ray or optical spectral excesses are further potential signatures of ultra-high-energy cosmic ray production in GRBs.

• OSTI ID: 21454900
• Journal Information: Astrophysical Journal Letters, Vol. 725, Issue 2; Other Information: DOI: 10.1088/2041-8205/725/2/L121; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASTROPHYSICS
COMPUTERIZED SIMULATION
COSMIC GAMMA BURSTS
ELECTRONS
EMISSION
EXTRAPOLATION
MONTE CARLO METHOD
PHOTONS
POSITRONS
PROTONS
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BARYONS
BOSONS
CALCULATION METHODS
COSMIC RADIATION
ELEMENTARY PARTICLES
FERMIONS
HADRONS
IONIZING RADIATIONS
LEPTONS
MASSLESS PARTICLES
MATHEMATICAL SOLUTIONS
MATTER
NUCLEONS
NUMERICAL SOLUTION
PHYSICS
PRIMARY COSMIC RADIATION
RADIATIONS
SIMULATION