1. The nature of dark gamma-ray bursts.
- Author
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Greiner, J., Krühler, T., Klose, S., Afonso, P., Clemens, C., Filgas, R., Hartmann, D. H., Yoldaş, A. Küpcü, Nardini, M., Olivares, F. E., Rau, A., Rossi, A., Schady, P., and Updike, A.
- Subjects
GAMMA ray bursts ,AFTERGLOW (Physics) ,ASTRONOMICAL observations ,REDSHIFT ,X-ray telescopes ,INFRARED radiation ,ASTROPHYSICS - Abstract
We use the afterglow detection statistics of the systematic follow-up observations performed with GROND since mid-2007 in order to derive the fraction of 'dark bursts' according to different methods, and to distinguish between various scenarios for 'dark bursts'. For long-duration Swift bursts with a detected X-ray afterglow, we achieve a 90% (35/39) detection rate of optical/NIR afterglows whenever our observations started within less than 240 min after the burst. Complementing our GROND data with Swift/XRT spectra we construct broad-band spectral energy distributions and derive rest-frame extinctions. We detect 25-40% 'dark bursts', depending on the definition used. The faint optical afterglow emission of 'dark bursts' is mainly due to a combination of two contributing factors: (i) moderate intrinsic extinction at moderate redshifts, and (ii) about 22% of 'dark' bursts at redshift >5. [ABSTRACT FROM AUTHOR]
- Published
- 2011
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