Vink 2007 大麦云中WR星的金属丰度较低

主要内容:
一般认为WR星是长暴的前身星，但要求WR星的金属丰度较低，因为金属丰度高，星风损失大，同时角动量损失也大，导致WR星的转动较慢而不能形成伽玛暴（为什么转动慢就不能形成伽玛暴？）。不过对大麦云的WR星巡天发现其金属丰度是较低的。

精彩摘抄:


文章信息:
Constraining GRB progenitor models by probing Wolf-Rayet wind geometries in the Large Magellanic Cloud

Authors: Jorick S. Vink (Armagh Observatory)

(Submitted on 20 Apr 2007)

Abstract: The favoured progenitors of long-duration gamma-ray bursts (GRBs) are rapidly rotating Wolf-Rayet (WR) stars. However, most Galactic WR stars are slow rotators, as stellar winds are thought to remove angular momentum. This poses a challenge to the collapsar model. Recent observations indicate that GRBs occur predominately in low metallicity (Z) environments, which may resolve the problem: lower Z leads to less mass loss, which may inhibit angular momentum removal, allowing WR stars to remain rotating rapidly until collapse. We wish to determine whether low Z WR stars rotate on average more rapidly than Galactic WR stars, and perform a Very Large Telescope (VLT) linear spectropolarimetry survey of WR stars in the low Z environment of the Large Magellanic Cloud (LMC) and compare our results with the Galactic sample. We find that only 2 out of 13 (i.e. 15%) of LMC WR stars show line polarization effects, compared to a similarly low fraction of ~15-20% for Galactic WR stars. The low incidence of line polarization effects in LMC WR stars suggests that the threshold metallicity where significant differences in WR rotational properties occur is below that of the LMC (Z ~ 0.5 Zsun), possibly constraining GRB progenitor channels to this upper metallicity.

Comments:

Accepted for A&A

Subjects:

Astrophysics (astro-ph)

Cite as:

arXiv:0704.2690v1 [astro-ph]