Very Early Optical Afterglows of Gamma‐Ray Bursts: Evidence for Relative Paucity of Detection
نویسندگان
چکیده
منابع مشابه
Early Optical Afterglows from Wind-Type Gamma-Ray Bursts
We study prompt optical emission from reverse shocks in the wind-type gamma-ray bursts. The emission is evaluated in both the thick and thin shell regimes. We discuss the angular time delay effect and the post-shock evolution of the fireball ejecta, which determine the decay index of the prompt optical emission and the duration of the radio flare. We discuss distinct emission signatures of the ...
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The first gamma-ray burst (GRB) for which an optical afterglow was observed was GRB 970228 [1, 2]. The first redshift for a GRB came from the optical afterglow of GRB 970508 [3, 4]. The inferred redshift for GRB 970508 was z = 0.835, which demonstrated that GRBs have cosmological origins and required that the bursts have isotropic equivalent energies of 10–10 erg, which was difficult to explain...
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The interaction of a relativistic fireball with its ambient medium is described through two shocks: a reverse shock that propagates into the fireball, and a forward shock that propagates into the medium. The observed optical flash of GRB 990123 has been considered to be the emission from such a reverse shock. The observational properties of afterglows suggest that the progenitors of some GRBs m...
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Based on the refined dynamical model proposed by us earlier for beamed γ-ray burst ejecta, we carry out detailed numerical procedure to study those γray bursts with rapidly fading afterglows (i.e., ∼ t). It is found that optical afterglows from GRB 970228, 980326, 980519, 990123, 990510 and 991208 can be satisfactorily fitted if the γ-ray burst ejecta are highly collimated, with a universal ini...
متن کاملEmission Spectra in the Very Early Afterglows of Gamma - Ray Bursts
We calculate the spectra of inverse Compton (IC) emissions in gamma-ray burst (GRB) shocks produced when relativistic ejecta encounters the external interstellar medium, assuming a broken power-law approximation to the synchrotron seed spectrum. Four IC processes, including the synchrotron self-Compton (SSC) processes in GRB forward and reverse shocks, and two combined-IC processes (i.e. scatte...
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ژورنال
عنوان ژورنال: The Astrophysical Journal
سال: 2006
ISSN: 0004-637X,1538-4357
DOI: 10.1086/508481