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Astron. Astrophys. 359, L23-L26 (2000)

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Letter to the Editor

Unusually rapid variability of the GRB000301C optical afterglow  *

N. Masetti 1, C. Bartolini 2, S. Bernabei 3, A. Guarnieri 2, E. Palazzi 1, E. Pian 1, A. Piccioni 2, A.J. Castro-Tirado 4,5, J.M. Castro Cerón 6, L. Verdes-Montenegro 4, R. Sagar 7, V. Mohan 7, A.K. Pandey 7, S.B. Pandey 7, H. Bock 8, J. Greiner 9, S. Benetti 10, R.A.M.J. Wijers 11, G.M. Beskin 12 and J. Gorosabel 13

1 Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, 40129 Bologna, Italy
2 Universitá di Bologna, Dipartimento di Astronomia, Via Ranzani 1, 40127 Bologna, Italy
3 Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna, Italy
4 IAA-CSIC, P.O. Box 03004, 18180, Granada, Spain
5 LAEFF-INTA, Madrid, Spain
6 Real Instituto y Observatorio de la Armada, 11110 San Fernando Naval, Cádiz, Spain
7 Uttar Pradesh State Observatory, Manora Peak, Nainital, 263 129, India
8 Landessternwarte Heidelberg, Heidelberg, Germany
9 Astrophysikalisches Institut, 14482 Potsdam, Germany
10 TNG Observatory, Canary Islands, Spain
11 Department of Physics & Astronomy, SUNY, Stony Brook, NY 11794-3800, USA
12 Special Astrophysical Observatory of RAS, Nizhnij Arkhyz, Karachai-Cherkessia, 357147 Russia
13 Danish Space Research Institute, Copenhagen, Denmark

Received 14 April 2000 / Accepted 27 June 2000


We present BVRI light curves of the afterglow of GRB000301C, one of the brightest ever detected at a day time scale interval after GRB trigger. The monitoring started 1.5 days after the GRB and ended one month later. Inspection of the extremely well sampled R band light curve and comparison with BVI data has revealed complex behavior, with a long term flux decrease and various short time scale features superimposed. These features are uncommon among other observed afterglows, and might trace either intrinsic variability within the relativistic shock (re-acceleration and re-energization) or inhomogeneities in the medium in which the shock propagates.

Key words: gamma rays: bursts

* Based on observations collected at the Bologna Astronomical Observatory in Loiano, Italy and at the TNG, Canary Islands, Spain

Send offprint requests to: Nicola Masetti, masetti@tesre.bo.cnr.it

© European Southern Observatory (ESO) 2000

Online publication: July 13, 2000