‘Long’ γ-ray bursts (GRBs) are commonly accepted to originate in the explosion of particularly massive stars, which give rise to highly relativistic jets. Inhomogeneities in the expanding flow result in internal shock waves that are believed to produce the γ-rays we see1,2. As the jet travels further outward into the surrounding circumstellar medium, ‘external’ shocks create the afterglow emission seen in the X-ray, optical and radio bands1,2. Here we report observations of the early phases of the X-ray emission of five GRBs. Their X-ray light curves are characterised by a surprisingly rapid fall-off for the first few hundred seconds, followed by a less rapid decline lasting several hours. This steep decline, together with detailed spectral properties of two particular bursts, shows that violent shock interactions take place in the early jet outflows.
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Mészáros, P. & Rees, M. Optical and long-wavelength afterglow from gamma-ray bursts. Astrophys. J. 476, 232–237 (1999)
Sari, R. & Piran, T. GRB 990123: The optical flash and the fireball model. Astrophys. J. 517, L109–L112 (1999)
Ford, L. A. et al. BATSE observations of gamma-ray burst spectra. 2: Peak energy evolution in bright, long bursts. Astrophys. J. 439, 307–321 (1995)
Frontera, F. et al. Spectral properties of the prompt X-ray emission and afterglow from the gamma-ray burst of 1997 February 28. Astrophys. J. 439, L67–L70 (1998)
Zhang, B. & Mészáros, P. Gamma-ray bursts: progress, problems, and prospects. Int. J. Mod. Phys. 19, 2385–2472 (2004)
Piran, T. The physics of gamma-ray bursts. Rev. Mod. Phys. 76, 1143–1210 (2005)
Piro, L. et al. Evidence for a late-time outburst of the X-ray afterglow of GRB970508 from BeppoSAX. Astron. Astrophys. 331, L41–L44 (1998)
Giblin, T. W. et al. Evidence for an early high-energy afterglow observed with BATSE from GRB 980923. Astrophys. J. 524, L47–L50 (1999)
Burenin, R. A. et al. GRANAT/SIGMA observation of GRB 920723 soft gamma-ray afterglow. Astron. Astrophys. 344, L53–L56 (1999)
Piro, L. et al. Probing the environment in gamma-ray bursts: The case of an X-ray precursor, afterglow late onset and wind versus constant density profile in GRB011121 and GRB011211. Astrophys. J. 623, 314–324 (2005)
Akerlof, C. et al. Observations of contemporaneous optical radiation from a gamma-ray burst. Nature 398, 400–402 (1999)
Fox, D. W. et al. Discovery of early optical emission from GRB021211. Astrophys. J. 586, L5–L8 (2003)
Gehrels, N. et al. The Swift gamma-ray burst mission. Astrophys. J. 611, 1005–1020 (2004)
Burrows, D. N. et al. Swift X-ray telescope and Very Large Telescope observations of the afterglow of GRB 041223. Astrophys. J. 622, L85–L88 (2005)
Campana, S. et al. Swift observations of GRB050128: the early X-ray afterglow. Astrophys. J. 625, L23–L26 (2005)
Burrows, D. N. et al. The Swift X-ray telescope. Space Sci. Rev. (in the press)
Barthelmy, S. D. et al. The Burst Alert Telescope (BAT) on the Swift MIDEX mission. Space Sci. Rev. (in the press)
Sato, G. et al. GRB050126: Bursts parameters measured by BAT. GCN Circ. 2987 (2005)
Hullinger, D. et al. GRB050219: Swift-BAT detection of a burst. GCN Circ. 3038 (2005)
McMahon, E., Kumar, P. & Panaitescu, A. Prompt gamma-ray and early afterglow emission in the external shock model. Mon. Not. R. Astron. Soc. 354, 915–923 (2004)
Mészáros, P. & Rees, M. J. Collapsar jets, bubbles, and Fe lines. Astrophys. J. 556, L37–L40 (2001)
Ramirez-Ruiz, E., Celotti, A. & Rees, M. J. Events in the life of a cocoon surrounding a light, collapsar jet. Mon. Not. R. Astron. Soc. 337, 1349–1356 (2002)
Rees, M. J. & Mészáros, P. Dissipative photosphere models of gamma-ray bursts and X-ray flashes. Astrophys. J. (in the press); 〈preprint at http://arXiV.org/astro-ph/0412702〉 (2005)
Kumar, P. & Piran, T. Energetics and luminosity function of gamma-ray bursts. Astrophys. J. 535, 152–157 (2000)
Kumar, P. & Panaitescu, A. Afterglow emission from naked gamma-ray bursts. Astrophys. J. 541, L51–L54 (2000)
Vietri, M. A simple, stringent test on the nature of GRB progenitors. Astropart. Phys. 14, 211–215 (2000)
Roming, P. W. et al. The Swift ultra-violet/optical telescope. Space Sci. Rev. (in the press)
Berger, E. et al. The discovery of the optical and near-IR afterglows of the first Swift gamma-ray bursts. Astrophys. J. (in the press); 〈preprint at http://arXiV.org/astro-ph/0502468〉 (2005)
Schady, P. et al. GRB050219a: No Swift UVOT detection of afterglow emission. GCN Circ. 3039 (2005)
Hill, J. E. et al. Read-out modes and automated operation of the Swift X-Ray telescope. Proc. SPIE 5165, 217–231 (2004)
We acknowledge support from ASI, NASA and PPARC.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
About this article
Cite this article
Tagliaferri, G., Goad, M., Chincarini, G. et al. An unexpectedly rapid decline in the X-ray afterglow emission of long γ-ray bursts. Nature 436, 985–988 (2005). https://doi.org/10.1038/nature03934
Experimental Astronomy (2021)
Astrophysics and Space Science (2020)
Space Science Reviews (2017)
Science China Physics, Mechanics and Astronomy (2010)
3-D Rpic Simulations of Relativistic Jets: Particle Acceleration, Magnetic Field Generation, and Emission
Astrophysics and Space Science (2007)