Letter to the Editor
Continuous optical monitoring during the prompt emission of GRB 060111B
CESR, Observatoire Midi-Pyrénées (CNRS - UPS), BP 4346, 31028 Toulouse Cedex 04, France e-mail: email@example.com
2 Observatoire de Haute-Provence, 04870 Saint Michel l'Observatoire, France
3 IASF - Roma/INAF, via fosso del cavaliere 100, 00133 Roma, Italy
4 LATT, Observatoire Midi-Pyrénées (CNRS - UPS), 14 avenue E. Belin, 31400 Toulouse, France
5 Observatoire de Genève, 1290 Sauverny, Switzerland
Accepted: 28 March 2006
Aims.We present the time-resolved optical emission of GRB 060111B during its prompt phase, measured with the TAROT robotic observatory. This is the first time that the optical emission from a gamma-ray burst has been continuously monitored with a temporal resolution of a few seconds during the prompt gamma-ray phase.
Methods.The temporal evolution of the prompt optical emission at the level of several seconds is used to provide a clue to the origin of this emission.
Results.The optical emission was found to decay steadily from our first measure, 28 s after the trigger, in contrast to the gamma-ray emission, which exhibits strong variability at the same time. This behaviour strongly suggests that the optical emission is due to the reverse shock.
Key words: gamma-rays: bursts
© ESO, 2006