Multiband Modeling of Two Unusual GRB Afterglows: GRB 050319 (wind to ISM Transition in View ?) and GRB 050401 (another case for Double Jet)

GRB 050319 (z = 3.24) and GRB 050401 (z = 2.9) are long duration and distant GRBs. Their afterglows show unusual and interesting features. We have modeled these afterglows using Fireball Model. We show that GRB 050401 afterglow provides another case for 'Double Jet' at a redshift of 2.9. Afterglow of GRB 050319 shows a clear signature of "Wind-to-ISM transition" of circum-stellar medium which is an important high redshift testimony, of Collapser origin of ong duration GRBs.

Collapse of a Massive Star is assumed to be the most probable progenitor of GRBs. Such a star is expected to modify it's environment by stellar wind. The signature of such a circum-stellar ind medium on the evolution of a GRB afterglow has so far not been conclusively seen. We claim a clear signature of `wind to homogeneous interstellar medium transition' of circum-burst medium in the afterglow of GRB 050319.

We present a model for the multiband afterglow of GRB 050319 and show that the break seen in optical light curve at ~ 0.02 day is due to `wind to homogeneous interstellar medium transition' of circum-burst medium. In our knowledge, this is the first ever detection of such a transition. This can also serve as a confirmation of Massive Star Collapse scenario for GRB progenitors, independent of Supernova signatures.

We present optical observations of GRB 050401 using 104-cm Sampurnanand Telescope at ARIES, Nainital. We also present a re-analysis of X-ray data of GRB 050401 taken by Swift-XRT. Results of analysis of multiband data are presented.

We have modeled the multiband afterglow of GRB 050401 as a Two Component Jet model interpreting the break in the X-ray light curve as being due to lateral expansion of the narrow collimated outflow which is dominant in X rays. The Optical afterglow is due to major contribution from a wider jet component. Our model reproduces all the observed features of the multiband afterglow of GRB 050401.

 

Fecha: 
19/10/2006 - 14:00
Conferenciante: 
Atish P. Kamble
Filiación: 
Raman Research Institute, India


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