Shen 2009 用瞬时辐射的光学流量限制暴本身的辐射半径

主要内容:
假设瞬时光学光子和伽玛光子来自相同的电子的同步辐射, 考虑光学流量应该和同步自吸收(即黑体低频段)一致, 可以给出半径和Gamma, B的关系, 得到对R的限制.

R > 10^14 (Gamma/300)^3/4 (B/10^5 G)^1/4 cm.

用了 GRBs - 041219A, 050820A, 051111 and 061121. 没有包括080319B.

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Title:		Prompt optical emission and synchrotron self-absorption constraints on emission site of GRBs
Authors:		Shen, Rong-Feng; Zhang, Bing
Publication:		eprint arXiv:0906.2597
Publication Date:		06/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		13 pages, 4 figures, accepted for publication on MNRAS
Bibliographic Code:		2009arXiv0906.2597S

Abstract

We constrain the distance of the Gamma-Ray Burst (GRB) prompt emission site from the explosion centre, R, by determining the location of the electron's self absorption frequency in the GRB prompt optical-to-X/gamma-ray spectral energy distribution, assuming that the optical and the gamma-ray emissions are among the same synchrotron radiation continuum of a group of hot electrons. All possible spectral regimes are considered in our analysis. The method has only two assumed parameters, namely, the bulk Lorentz factor of the emitting source Gamma, and the magnetic field strength B in the emission region (with a weak dependence). We identify a small sample of 4 bursts that satisfy the following three criteria: (1) they all have simultaneous optical and gamma-ray detections in multiple observational time intervals; (2) they all show temporal correlations between the optical and gamma-ray light curves; and (3) the optical emission is consistent with belonging to the same spectral component as the gamma-ray emission. For all the time intervals of these 4 bursts, it is inferred that R \geq 10^{14} (Gamma/300)^{3/4} (B/10^5 Gauss)^{1/4} cm. For a small fraction of the sample, the constraint can be pinned down to R \approx 10^{14} - 10^{15} cm for Gamma ~ 300. For a second sample of bursts with prompt optical non-detections, only upper limits on R can be obtained. We find no inconsistency between the R-constraints for this non-detection sample and those for the detection sample.

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