GROND coverage of the main peak of Gamma-Ray Burst 130925A
Abstract
Prompt or early optical emission in gamma-ray bursts is notoriously difficult to measure, and observations of the dozen cases show a large variety of properties. Yet, such early emission promises to help us achieve a better understanding of the GRB emission process(es). We performed dedicated observations of the ultra-long duration (T90 about 7000 s) GRB 130925A in the optical/near-infrared with the 7-channel "Gamma-Ray Burst Optical and Near-infrared Detector" (GROND) at the 2.2m MPG/ESO telescope. We detect an optical/NIR flare with an amplitude of nearly 2 mag which is delayed with respect to the keV--MeV prompt emission by about 300--400 s. The decay time of this flare is shorter than the duration of the flare (500 s) or its delay. While we cannot offer a straightforward explanation, we discuss the implications of the flare properties and suggest ways toward understanding it.
Keywords
Cite
@article{arxiv.1407.4210,
title = {GROND coverage of the main peak of Gamma-Ray Burst 130925A},
author = {J. Greiner and H. -F. Yu and T. Krühler and D. D. Frederiks and A. Beloborodov and P. N. Bhat and J. Bolmer and H. van Eerten and R. L. Aptekar and J. Elliott and S. V. Golenetskii and J. F. Graham and K. Hurley and D. A. Kann and S. Klose and A. Nicuesa Guelbenzu and A. Rau and P. Schady and S. Schmidl and V. Sudilovsky and D. S. Svinkin and M. Tanga and M. V. Ulanov and K. Varela and A. von Kienlin and X. -L. Zhang},
journal= {arXiv preprint arXiv:1407.4210},
year = {2014}
}
Comments
9 pages, 9 figures, accepted for publ. in A&A