Yu 2007 Shallow decay相的星风泡解释

主要内容:
用磁星主导的外流星风泡作为能量注入的机制，星风的反向激波解释早期余辉的平降阶段。

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文章信息:
Shallow decay phase of GRB X-ray afterglows from relativistic wind bubbles

Authors: Yun-Wei Yu, Zi-Gao Dai

(Submitted on 8 May 2007)

Abstract: The postburst object of a GRB is likely to be a highly magnetized, rapidly rotating compact object (e.g., a millisecond magnetar), which could produce an ultrarelativistic electron-positron-pair wind. The interaction of such a wind with an outwardly expanding fireball ejected during the burst leads to a relativistic wind bubble (RWB). We numerically calculate the dynamics and radiative properties of RWBs and use this model to explain the shallow decay phase of the early X-ray afterglows observed by Swift. We find that RWBs can fall into two types: forward-shock-dominated and reverse-shock-dominated bubbles. Their radiation during a period of $\sim 10^{2}-10^{5}$ seconds is dominated by the shocked medium and the shocked wind, respectively, based on different magnetic energy fractions of the shocked materials. For both types, the resulting light curves always have a shallow decay phase. In addition, we provide an example fit to the X-ray afterglows of GRB 060813 and GRB 060814 and show that they could be produced by forward-shock-dominated and reverse-shock-dominated bubbles, respectively. This implies that, for some early afterglows (e.g., GRB 060814), the long-lasting reverse shock emission is strong enough to explain their shallow decay phase.

Comments:

5 pages, 4 figures, Accepted for Publication in A&A

Subjects:

Astrophysics (astro-ph)

Cite as:

arXiv:0705.1108v1 [astro-ph]