Bietenholz 2007 SN 2001em没有成协的伽玛暴

主要内容:
曾经有人说（如Granot）SN 2001em有一个不对着我们的喷流，预言这个喷流由于近光速运动，会在几年后离中心较远（成像的图上）。此文是继前一文(Chugai 2006,ApJ 641, 1051)之后又说没有看到这个相对论性的喷流。

精彩摘抄:
光变曲线
image

文章信息:

arXiv:0706.3344 [ps, pdf, other]

Title: SN 2001em: No Jet-Driven Gamma Ray Burst Event

Authors: M. F. Bietenholz, N. Bartel

Comments: 5 pages, 2 figs, accepted for publication in ApJ Letters

Subjects: Astrophysics (astro-ph)

We report on our second-epoch VLBI and VLA observations of the Type Ib/c supernova 2001em, five years after the explosion. SN 2001em is the first Type Ib/c supernova for which VLBI observations have been carried out. It was suggested that SN 2001em might be a jet-driven gamma ray burst (GRB), with the jet oriented near the plane of the sky, which would entail relativistic expansion or motion. Our VLBI image shows that SN 2001em is still unresolved five years after the explosion. For a distance of 83 Mpc (H_0 = 70 km/s/Mpc), the nominal expansion velocity is 5800 +/- 10,000 km/s, and the proper motion is 33,000 +/- 34,000 km/s. Our values are inconsistent with either relativistic expansion or motion, but are consistent with the non-relativistic expansion speeds and small proper motions seen in other supernovae. In particular these values are consistent with radio emission from SN 2001em being due to normal, non-relativistic supernova ejecta interacting with the circumstellar medium. Our VLA observations show a power-law decay in flux density since the time of the peak in the 8.4 GHz radio lightcurve in ~2003.