Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006sf2a.conf..145g&link_type=abstract
SF2A-2006: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics Eds.: D. Barret, F. Casoli, G.
Astronomy and Astrophysics
Astrophysics
Scientific paper
GRB 060105 was detected by Swift and Konus-Wind. This event was particularly bright with a bolometric fluence of 7.9× 10-5 erg cm-2 in the 18 keV-2 MeV Konus energy range. GRB 060105 could be a bright high-redshift (z>3) GRB, and possibly one of the most powerful GRBs ever detected with a jet geometry-corrected Gamma-ray energy of ˜ 7.3+2.8-2.9 × 1051 erg, using a pseudo-redshift of pz=4.0± 1.3 and the Ghirlanda relation. The X-ray light-curve of the burst first exhibits a long shallow decay lasting at least 1100 s showing a spectral hardening, followed by three other temporal segments: (i) a steep temporal decay (α˜ 3.2) from ˜ 4000 s to ˜ 2.5 × 10^4 s after the BAT trigger (T_0), (ii) a shallow decay (α˜ 0.8) up to T_0+6.8× 10^4 s, and (iii) a steep decay (α˜ 2.2) showing a late spectral softening after T_0+10^5 s. The initial long shallow decay is unusual for most of the GRBs (except the peculiar event XRF 060218), as well as the late steep decay during the segment (i) of the X-ray light-curve. We argue that the shallow decay is a part of an X-ray flare likely produced by late internal shock or alternatively possibly produced by the shock breakout of a jet cocoon from the envelope of a massive star. The segment (i) of the X-ray light-curve is naturally interpreted as due to curvature effect emission after the shock crossing. The segments (ii) and (iii) can be interpreted as due to the forward shock emission from the jet only in the case of the slow cooling ISM afterglow model. The electron distribution is unusually steep with p˜ 2.8-5.5 for this burst. We show that during the forward-shock-dominated part of the light-curve, the drop of the cooling frequency through the XRT band with time accounts for thethe late spectral softening seen in our data.
Godet Olivier
O'Brien Thomas P.
Osborne Julian Paul
Page Kim L.
Pal'shin Valentin
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