GRB 051210: Swift detection of a short gamma ray burst

Aims. The short/hard GRB 051210 was detected and located by the Swift-BAT instrument and rapidly pointed towards by the narrow field instruments. The XRT was able to observe a bright, rapidly fading X-ray emission. We present the analysis of the prompt and afterglow emission of this event. Methods. The BAT spectrum is a power-law with photon index 1.0 ± 0.3. The X-ray light curve decays with slope -2.58 ± 0.11 and shows a small flare in the early phases. The spectrum can be described with a power law with photon index 1.54 ± 0.16 and absorption (7.5 +4.3 -3.2 )×10 20 cm -2 . Results. We find that the X-ray emission is consistent with the hypothesis that we are observing the curvature effect of a GRB that occurred in a low density medium, with no detectable afterglow attributable to an external shock. We estimate the density of the circumburst medium to be lower than 3 x 10 -3 cm -3 . We also discuss different hypothesis on the possible origin of the flare.

[1]  T. Sakamoto,et al.  GRB 050911: A Black Hole-Neutron Star Merger or a Naked GRB , 2005, astro-ph/0512358.

[2]  Bing Zhang,et al.  Flares in Long and Short Gamma-Ray Bursts: A Common Origin in a Hyperaccreting Accretion Disk , 2005, astro-ph/0511506.

[3]  J.-L. Atteia,et al.  Discovery of the short γ-ray burst GRB 050709 , 2005, Nature.

[4]  M. M. Kasliwal,et al.  The afterglow of GRB 050709 and the nature of the short-hard γ-ray bursts , 2005, Nature.

[5]  D. Proga,et al.  Linearly Polarized X-Ray Flares following Short Gamma-Ray Bursts , 2005, astro-ph/0509019.

[6]  P. O’Brien,et al.  Gamma-Ray Bursts: Restarting the Engine , 2005, astro-ph/0508126.

[7]  N. Gehrels,et al.  Bright X-ray Flares in Gamma-Ray Burst Afterglows , 2005, Science.

[8]  T. Sakamoto,et al.  A short γ-ray burst apparently associated with an elliptical galaxy at redshift z = 0.225 , 2005, Nature.

[9]  Melvyn B. Davies,et al.  The ultimate outcome of black hole–neutron star mergers , 2004, astro-ph/0409681.

[10]  Alan A. Wells,et al.  The Swift Gamma-Ray Burst Mission , 2004, astro-ph/0405233.

[11]  Scott D. Barthelmy,et al.  The Burst Alert Telescope (BAT) on the SWIFT Midex Mission , 2004, SPIE Optics + Photonics.

[12]  C. Dermer.  Curvature Effects in Gamma-Ray Burst Colliding Shells , 2004, astro-ph/0403508.

[13]  Richard M. Ambrosi,et al.  Readout modes and automated operation of the Swift X-ray Telescope , 2003, SPIE Optics + Photonics.

[14]  Peter W. A. Roming,et al.  The Swift Ultra-Violet/Optical Telescope , 2002, SPIE Optics + Photonics.

[15]  D. Watson,et al.  The Swift X-Ray Telescope , 1999, SPIE Optics + Photonics.

[16]  K. Pedersen,et al.  A very energetic supernova associated with the γ-ray burst of 29 March 2003 , 2003, Nature.

[17]  Warren R. Brown,et al.  Spectroscopic Discovery of the Supernova 2003dh Associated with GRB 030329 , 2003, astro-ph/0304173.

[18]  A. Panaitescu,et al.  Properties of Relativistic Jets in Gamma-Ray Burst Afterglows , 2001, astro-ph/0109124.

[19]  E. Ramirez-Ruiz,et al.  Possible detection of hard X-ray afterglows of short $\gamma$-ray bursts , 2001, astro-ph/0110215.

[20]  S. Djorgovski,et al.  Beaming in Gamma-Ray Bursts: Evidence for a Standard Energy Reservoir , 2001, astro-ph/0102282.

[21]  Re'em Sari,et al.  On the Synchrotron Self-Compton Emission from Relativistic Shocks and Its Implications for Gamma-Ray Burst Afterglows , 2000, astro-ph/0005253.

[22]  A. Panaitescu,et al.  Afterglow Emission from Naked Gamma-Ray Bursts , 2000, astro-ph/0006317.

[23]  S. Djorgovski,et al.  The unusual afterglow of the γ-ray burst of 26 March 1998 as evidence for a supernova connection , 1999, Nature.

[24]  S. Djorgovski,et al.  The unusual afterglow of GRB 980326: evidence for the gamma-ray burst/supernova connection , 1999, astro-ph/9905301.

[25]  T. Piran,et al.  Spectra and Light Curves of Gamma-Ray Burst Afterglows , 1997, astro-ph/9712005.

[26]  C. Kouveliotou,et al.  Identification of two classes of gamma-ray bursts , 1993 .

[27]  S. Woosley.  Gamma-ray bursts from stellar mass accretion disks around black holes , 1993 .

[28]  J. Dickey,et al.  H I in the Galaxy , 1990 .

[29]  M. Livio,et al.  Nucleosynthesis, neutrino bursts and γ-rays from coalescing neutron stars , 1989, Nature.

[30]  J. P. Norris,et al.  Frequency of fast, narrow γ-ray bursts , 1984, Nature.

[31]  Yu. A. Gur'yan,et al.  Catalog of cosmic gamma-ray bursts from the KONUS experiment data , 1981 .