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posted on 07.05.2015, 14:08 by A. J. Levan, N. R. Tanvir, R. L. C. Starling, K. Wiersema, K. L. Page, D. A. Perley, S. Schulze, G. A. Wynn, R. Chornock, J. Hjorth, S. B. Cenko, A. S. Fruchter, P. T. O'Brien, G. C. Brown, R. L. Tunnicliffe, D. Malesani, P. Jakobsson, D. Watson, E. Berger, D. Bersier, B. E. Cobb, S. Covino, A. Cucchiara, A. de Ugarte Postigo., D. B. Fox, A. Gal-Yam, P. Goldoni, J. Gorosabel, L. Kaper, T. Kruehler, R. Karjalainen, J. P. Osborne, E. Pian, R. Sanchez-Ramirez, B. Schmidt, I. Skillen, G. Tagliaferri, C. Thoene, O. Vaduvescu, R. A. M. J. Wijers, B. A. Zauderer
We present comprehensive multiwavelength observations of three gamma-ray bursts (GRBs) with durations of several thousand seconds. We demonstrate that these events are extragalactic transients; in particular, we resolve the long-standing conundrum of the distance of GRB 101225A (the "Christmas-day burst"), finding it to have a redshift z = 0.847 and showing that two apparently similar events (GRB 111209A and GRB 121027A) lie at z = 0.677 and z = 1.773, respectively. The systems show extremely unusual X-ray and optical light curves, very different from classical GRBs, with long-lasting, highly variable X-ray emission and optical light curves that exhibit little correlation with the behavior seen in the X-ray. Their host galaxies are faint, compact, and highly star-forming dwarf galaxies, typical of "blue compact galaxies." We propose that these bursts are the prototypes of a hitherto largely unrecognized population of ultra-long GRBs, which while observationally difficult to detect may be astrophysically relatively common. The long durations may naturally be explained by the engine-driven explosions of stars of much larger radii than normally considered for GRB progenitors, which are thought to have compact Wolf-Rayet progenitor stars. However, we cannot unambiguously identify supernova signatures within their light curves or spectra. We also consider the alternative possibility that they arise from the tidal disruption of stars by massive black holes and conclude that the associated timescales are only consistent with the disruption of compact stars (e.g., white dwarfs) by black holes of relatively low mass (<105 M ☉).


We thank D. A. Kann and the GROND team for sharing their photometric calibration and Jamie Kennea for providing information on the Swift slew strategy. A.J.L. acknowledges support from the Science and Technology Facilities Council (STFC, under grant ID ST/I001719/1) and is grateful to the Leverhulme Trust for a Philip Leverhulme Prize award. N.R.T., K.W., and P.T.O. thank STFC for support (grant ID ST/H001972/ 1). R.L.C.S. is supported by a Royal Society Dorothy Hodgkin Fellowship. The Dark Cosmology Centre is supported by the DNRF. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 288.D-5027. Support for programs 11734, 12438, and 12786 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5- 26555. Support for D.P. is provided by NASA through Hubble Fellowship grant HST-HF-51296.01-A awarded by the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., for NASA, under contract NAS 5-26555. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministerio da Ci ´ encia, Tecnologia e Inova¸ ˆ cao˜ (Brazil), and Ministerio de Ciencia, Tecnolog´ıa e Innovacion´ Productiva (Argentina). These observations were obtained as part of programme IDs GN-2010B-Q-7, GN-2011A-Q-4, GS- 2011B-Q-7, GN-2011B-Q-34, and GS-2012A-Q-25. This work was made possible by contributions from Iniciativa Cientifica Milenio grant P10-064-F (Millennium Center for Supernova Science), wit



Astrophysical Journal, 2014, 781 (1), pp. ?-? (22)

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/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy


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