Open AccessGRB 060418 and 060607A: the medium surrounding the progenitor and the weak reverse shock emission
Author(s) -
Jin Z. P.,
Fan Y. Z.
Publication year - 2007
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2007.11836.x
Subject(s) - physics , afterglow , gamma ray burst , astrophysics , shock (circulatory) , light curve , synchrotron , shock wave , astronomy , optics , mechanics , medicine
We constrain the circumburst medium profile with the rise behaviour of the very early afterglow light curves of gamma‐ray bursts (GRBs). Using this method, we find a constant and low‐density medium profile for GRB 060418 and GRB 060607A, which is consistent with the inference from the late afterglow data. In addition, we show that the absence of the infrared flashes in these two afterglows is consistent with the standard hydrodynamical external reverse shock model. Although a highly magnetized model can explain the data, it is no longer demanded. A weak reverse shock in the standard hydrodynamical model is achievable if the typical synchrotron frequency is already below the band at the shock‐crossing time.