Multiwavelength study of the very long GRB 020410

¹ IASF - CNR, via U. La Malfa 153, 90146 Palermo, Italy e-mail: nicastro@pa.iasf.cnr.it
² SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
³ Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands
⁴ IASF - CNR, via P. Gobetti 101, 40129 Bologna, Italy
⁵ Ioffe Institute, 26 Polytekhnicheskaya, St. Petersburg 194021, Russian Federation
⁶ Instituto de Astrofísica de Andalucía (IAA-CSIC), PO Box 03004, 18080 Granada, Spain
⁷ Institute of Astronomy, University of Cambridge, Madingley Road, UK CB3 0HA Cambridge, UK
⁸ IASF - CNR, via Fosso del Cavaliere, 00131 Roma, Italy
⁹ Osservatorio Astr. di Trieste, via GB Tiepolo 11, 34131 Trieste, Italy
¹⁰ XMM-Newton Science Operations Centre, Villafranca del Castillo, PO Box 50727, 28080 Madrid, Spain
¹¹ Mt. John University Observatory, Canterbury University, New Zealand

Received: 24 March 2004
Accepted: 16 July 2004

Abstract

GRB 020410 is by far the longest γ-ray burst (with a duration of about 1600 s) to have been followed up from the X-ray through the radio regime. Afterglow emission was detected in X-rays and at optical wavelengths whereas no emission was detected at 8 GHz brighter than 120 μJy. The decaying X-ray afterglow, back-extrapolated to 11 h after the burst, had a flux of 7.9  10^-12 erg cm^-2 s^-1 (2–10 keV); the brightest detected so far. No direct redshift determination is available yet for this GRB, but according to the empirical relationship between the peak energy in the spectrum and the isotropic energy output, z is constrained in the range 0.9–1.5. The reconstructed optical afterglow light curve implies at least two breaks in the simple power law decay. This may be related to emergence of an SN, or refreshment of the external shock by a variation in the circumstellar medium. Considering the backward extrapolation of the 2–10 keV afterglow decay, the prompt lightcurve variability and its spectral evolution, we conclude that the long duration of this event is due to a prolonged activity of the “central engine”.