Swift Panchromatic Observations of the Bright Gamma-Ray Burst GRB 050525a

A.~J. Blustin, D. Band, S. Barthelmy, P. Boyd, M. Capalbi, S.~T. Holland, F.~E. Marshall, K.~O. Mason, M. Perri, T. Poole, P. Roming, S. Rosen, P. Schady, M. Still, B. Zhang, L. Angelini, L. Barbier, A. Beardmore, A. Breeveld, D.~N. BurrowsJ.~R. Cummings, J. Cannizzo, S. Campana, M.~M. Chester, G. Chincarini, L.~R. Cominsky, A. Cucchiara, M. de Pasquale, E.~E. Fenimore, N. Gehrels, P. Giommi, M. Goad, C. Gronwall, D. Grupe, J.~E. Hill, D. Hinshaw, S. Hunsberger, K.~C. Hurley, M. Ivanushkina, J.~A. Kennea, H.~A. Krimm, P. Kumar, W. Landsman, V. La Parola, C.~B. Markwardt, K. McGowan, P. Mészáros, T. Mineo, A. Moretti, A. Morgan, J. Nousek, P.~T. O'Brien, J.~P. Osborne, K. Page, M.~J. Page, D.~M. Palmer, A.~M. Parsons, J. Rhoads, P. Romano, T. Sakamoto, G. Sato, G. Tagliaferri, J. Tueller, A.~A. Wells, N.~E. White

Research output: Contribution to journalArticlepeer-review

102 Citations (Scopus)

Abstract



The bright gamma-ray burst GRB 050525a has been detected with the Swift observatory, providing unique multiwavelength coverage from the very earliest phases of the burst. The X-ray and optical/UV afterglow decay light curves both exhibit a steeper slope ~0.15 days after the burst, indicative of a jet break. This jet break time combined with the total gamma-ray energy of the burst constrains the opening angle of the jet to be 3fdg2. We derive an empirical "time-lag" redshift from the BAT data of img1.gif = 0.69 ± 0.02, in good agreement with the spectroscopic redshift of 0.61. Prior to the jet break, the X-ray data can be modeled by a simple power law with index α = -1.2. However, after 300 s the X-ray flux brightens by about 30% compared to the power-law fit. The optical/UV data have a more complex decay, with evidence of a rapidly falling reverse shock component that dominates in the first minute or so, giving way to a flatter forward shock component at later times. The multiwavelength X-ray/UV/optical spectrum of the afterglow shows evidence for migration of the electron cooling frequency through the optical range within 25,000 s. The measured temporal decay and spectral indexes in the X-ray and optical/UV regimes compare favorably with the standard fireball model for gamma-ray bursts assuming expansion into a constant-density interstellar medium.
Original languageEnglish
Pages (from-to)901-913
Number of pages13
JournalAstrophysical Journal
Volume637
Issue number2
DOIs
Publication statusPublished - 1 Feb 2006

Keywords

  • Astrometry, Galaxies: Distances and Redshifts, Gamma Rays: Bursts, Shock Waves, X-rays: individual (GRB 050525a), Astrophysics

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