A link between prompt optical and prompt γ-ray emission in γ-ray bursts

The prompt optical emission that arrives with the γ-rays from a cosmic γ-ray burst (GRB) is a signature of the engine powering the burst, the properties of the ultra-relativistic ejecta of the explosion, and the ejecta's interactions with the surroundings. Until now, only GRB 990123 had been detected at optical wavelengths during the burst phase. Its prompt optical emission was variable and uncorrelated with the prompt γ-ray emission, suggesting that the optical emission was generated by a reverse shock arising from the ejecta's collision with surrounding material. Here we report prompt optical emission from GRB 041219a. It is variable and correlated with the prompt γ-rays, indicating a common origin for the optical light and the γ-rays. Within the context of the standard fireball model of GRBs, we attribute this new optical component to internal shocks driven into the burst ejecta by variations of the inner engine. The correlated optical emission is a direct probe of the jet isolated from the medium. The timing of the uncorrelated optical emission is strongly dependent on the nature of the medium.

[1]  G. Gisler,et al.  Observation of contemporaneous optical radiation from a γ-ray burst , 1999, Nature.

[2]  J. I. Katz.  LOW-FREQUENCY SPECTRA OF GAMMA-RAY BURSTS , 1993 .

[3]  M. Boettcher,et al.  GRB 990123: The Case for Saturated Comptonization , 1999, astro-ph/9903438.

[4]  J. M. Castro Cerón,et al.  A very energetic supernova associated with the gamma-ray burst of 29 March 2003. , 2003, Nature.

[5]  Ryan Chornock,et al.  The Early Light Curve of the Optical Afterglow of GRB 021211 , 2003, astro-ph/0302136.

[6]  C. Kouveliotou,et al.  The Fourth BATSE Gamma-Ray Burst Catalog (Revised) , 1999, astro-ph/9903205.

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

[8]  S. R. Kulkarni,et al.  Discovery of Early Optical Emission from GRB 021211 , 2003, astro-ph/0301377.

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

[10]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .

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

[12]  S. Barthelmy,et al.  An infrared flash contemporaneous with the γ-rays of GRB 041219a , 2005, Nature.

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

[14]  M. Rees,et al.  GRB 990123: reverse and internal shock flashes and late afterglow behaviour , 1999 .

[15]  A. Panaitescu,et al.  Analysis of two scenarios for the early optical emission of the gamma‐ray burst afterglows 990123 and 021211 , 2004 .

[16]  D. Schlegel,et al.  Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds , 1997, astro-ph/9710327.

[17]  J. van Paradijs,et al.  UvA-DARE ( Digital Academic Repository ) Gamma-Ray Burst afterglows , 2000 .

[18]  Eli Waxman,et al.  Gamma-Ray-Burst Afterglow: Supporting the Cosmological Fireball Model, Constraining Parameters, and Making Predictions , 1997, astro-ph/9704116.

[19]  Tsvi Piran,et al.  Predictions for the Very Early Afterglow and the Optical Flash , 1999, astro-ph/9901338.

[20]  Tsvi Piran,et al.  Early afterglow emission from a reverse shock as a diagnostic tool for gamma-ray burst outflows , 2004, astro-ph/0403461.

[21]  M. Rees,et al.  Optical and Long-Wavelength Afterglow from Gamma-Ray Bursts , 1996, astro-ph/9606043.

[22]  Bing Zhang,et al.  Gamma-Ray Burst Early Optical Afterglows: Implications for the Initial Lorentz Factor and the Central Engine , 2003 .

[23]  M. Feroci,et al.  Discovery of a Radio Flare from GRB 990123 , 1999, astro-ph/9903441.

[24]  E. Fenimore,et al.  RAPTOR: Closed‐Loop monitoring of the night sky and the earliest optical detection of GRB 021211 , 2004 .

[25]  W. T. Vestrand,et al.  The RAPTOR experiment: a system for monitoring the optical sky in real time , 2002, SPIE Astronomical Telescopes + Instrumentation.