Bietenholz 2008 VLBI Observations of SN 2008D

主要内容:
简单地说就是一正常超新星. 速度的upper limit是0.75 c.
和一般超新星的膨胀速度小于30, 000 km s−1也是一致的.

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Title:		VLBI Observations of SN 2008D
Authors:		Bietenholz, M. F.; Soderberg, A. M.; Bartel, N.
Publication:		eprint arXiv:0811.3173
Publication Date:		11/2008
Origin:		ARXIV
Keywords:		Astrophysics
Bibliographic Code:		2008arXiv0811.3173B

Abstract

We report on two epochs of VLBI observations of the Type Ib/c supernova SN 2008D, which was associated with the X-ray outburst XRF 080109, At our first epoch, at t=30 days after the explosion, we observed at 22 and 8.4 GHz, and at our second, at t=133 days, at 8.4 and 5.0 GHz. The VLBI observations allow us to accurately measure the source's size and position at each epoch, and thus constrain its expansion velocity and proper motion. We find the source at best marginally resolved at both epochs, allowing us to place a 3sigma upper limit of ~0.75c on the expansion velocity of a circular source. For an elongated source, our measurements are compatible with mildly relativistic expansion. However, our 3sigma upper limit on the proper motion is 4 micro-arcsec/day, corresponding to an apparent velocity of <0.6c,>c. Taken together, our measurements argue against the presence of any long-lived relativistic outflow in SN 2008D. On the other hand, our measurements are consistent with the non-relativistic expansion velocities of <30,000> Bibtex entry for this abstract Preferred format for this abstract (see Preferences)