Li 2007 SN 1998bw 的射电光变

主要内容:
作者认为是在星风环境下的激波,考虑同步自吸收。而两个峰的解释是第二个峰来自于能量注入。

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文章信息:
The Astrophysical Journal, 526:716-726, 1999 December 1
© 1999. The American Astronomical Society. All rights reserved. Printed in U.S.A.

Radio Supernova SN 1998bw and Its Relation to GRB 980425

Zhi-Yun Li and Roger A. Chevalier
Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903; zl4h@virginia.edu, rac5x@virginia.edu

ABSTRACT

SN 1998bw is an unusual Type Ic supernova that may be associated with the -ray burst GRB 980425. We use a synchrotron self-absorption model for its radio emission to deduce that the synchrotron-emitting gas is expanding into a circumstellar medium of approximately r^-2 density profile at a speed comparable to the speed of light. We assume that the efficiencies of production of relativistic electrons and magnetic field are constant through the evolution. The circumstellar density is consistent with that expected around the massive star core thought to be the progenitor of SN 1998bw. The explosion energy in material moving with velocity greater than 0.5c is 10⁴⁹ - (3 × 10⁵⁰) ergs, with some preference for the high values. The rise in the radio light curves observed at days 2040 is inferred to be the result of a rise in the energy of the blast wave by a factor of 2.5. Interaction with a jump in the ambient density is not consistent with the observed evolution. We infer that the boost in energy is from a shell of matter from the explosion that catches up with the decelerating shock front. Both the high explosion energy and the nature of the energy input to the blast wave are difficult to reconcile with energy input from the shock-accelerated high-velocity ejecta from a supernova. The implication is that there is irregular energy input from a central engine, which is the type of model invoked for normal -ray bursts. The link between SN 1998bw and GRB 980425 is thus strengthened.