A Comprehensive Study of GRB 070125, A Most Energetic Gamma‐Ray Burst

Abstract

We present a comprehensive multiwavelength analysis of the bright, long\nduration gamma-ray burst GRB 070125, comprised of observations in $\\gamma$-ray,\nX-ray, optical, millimeter and centimeter wavebands. Simultaneous fits to the\noptical and X-ray light curves favor a break on day 3.78, which we interpret as\nthe jet break from a collimated outflow. Independent fits to optical and X-ray\nbands give similar results in the optical bands but shift the jet break to\naround day 10 in the X-ray light curve. We show that for the physical\nparameters derived for GRB 070125, inverse Compton scattering effects are\nimportant throughout the afterglow evolution. While inverse Compton scattering\ndoes not affect radio and optical bands, it may be a promising candidate to\ndelay the jet break in the X-ray band. Radio light curves show rapid flux\nvariations, which are interpreted as due to interstellar scintillation, and are\nused to derive an upper limit of $2.4 \\times 10^{17}$ cm on the radius of the\nfireball in the lateral expansion phase of the jet. Radio light curves and\nspectra suggest a high synchrotron self absorption frequency indicative of the\nafterglow shock wave moving in a dense medium. Our broadband modeling favors a\nconstant density profile for the circumburst medium over a wind-like profile\n($R^{-2}$). However, keeping in mind the uncertainty of the parameters, it is\ndifficult to unambiguously distinguish between the two density profiles. Our\nbroadband fits suggest that \\event is a burst with high radiative efficiency\n($> 60 %$).\n