Astrophysics, abstract
astro-ph/0608313

From: Johan Peter Uldall Fynbo [view email]

Date: Tue, 15 Aug 2006 15:38:49 GMT (445kb)

A new type of massive stellar death: no supernovae from two nearby long gamma ray bursts

Authors: Johan P. U. Fynbo, Darach Watson, Christina C. Thoene, Jesper Sollerman, Joshua S. Bloom, Tamara M. Davis, Jens Hjorth, Pall Jakobsson, Uffe G. Joergensen, Arnaud Cassan, José María Castro Cerón, Javier Gorosabel, Tobias C. Hinse, Brian L. Jensen, Sylvio Klose, Daniel Kocevski, Daniel Perley, Enrico Ramirez-Ruiz, Maximilian D. Stritzinger, Paul Vreeswijk, Ralph A. M. Wijers, Kristian G. Woller, Marta Zub, Dong Xu

Comments: Submitted to Nature on July 7. Posted on Nature website July 12, see this http URL Revised on August 10

It is now accepted that long duration gamma-ray bursts (GRBs) are produced during the collapse of a massive star. The prevailing model (the collapsar) predicts that a broad-lined and luminous Type Ic core-collapse supernova (SN) accompanies every long-duration GRB. This association has been confirmed in observations of several nearby GRBs. Here we present observations of two nearby long-duration GRBs that challenge the prevailing model. In the GRBs 060505 and 060614 we demonstrate that no SN emission accompanied these bursts, down to limits hundreds of times fainter than the archetypal SN 1998bw that accompanied GRB 980425, and fainter than any Type Ic SN ever observed. Multi-band observations of the early afterglows, as well as spectroscopy of the GRB 060505 host galaxy, exclude the possibility of significant dust obscuration. Both GRBs are long-duration bursts, and we show that they lie in actively star-forming regions, typical of long GRBs. The absence of a SN to such deep limits is qualitatively different from all previous nearby long GRBs and suggests a new phenomenological type of massive stellar death.

http://arxiv.org/abs/astro-ph/0608313