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arXiv 1402.3701astro-ph.HE
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伽马射线暴光学余辉中反向激波发射的唯象

Phenomenology of Reverse-Shock Emission in the Optical Afterglows of Gamma Ray Bursts

J. Japelj, D. Kopac, S. Kobayashi, R. Harrison, C. Guidorzi, F. J. Virgili, C. G. Mundell, A. Melandri, A. Gomboc

摘要:

我们使用一个母样本的118伽马射线暴(GRB)余辉,已知的红移和宿主星系的灭绝,分离余辉和不占主导地位的反向激波发射的签名,并确定哪些物理条件导致一个突出的反向激波发射。我们确定了10个具有反向冲击特征的伽玛暴-伽玛暴990123,021004,021211,060908,061126,080319 B,081007,090102,090424和130427 A。通过模拟它们的光学余辉与反向和正向冲击解析光变曲线和使用蒙特卡罗模拟,我们估计的参数空间的物理量描述喷出物和环爆介质。我们发现,物理性质涵盖了广泛的参数空间,似乎没有集群周围的任何优惠值。通过对非RS主导的GRB大样本的静止坐标系光学、X射线和高能性质的比较,我们发现,在早期($<$ 1 ks),我们的逆激波主导的GRB样本的光谱光度、X射线余辉光度和$γ$射线能量输出与一般GRB样本没有显著差异。然而,以反向激波辐射为主的伽玛暴在后期($>$ 10 ks)比平均光学正向激波辐射要弱。我们发现,具有可识别的反向冲击分量的伽玛暴显示出高的磁化参数$R_{\mathrm{B}} = \varepsilon_{\rm B,r}/\varepsilon_{\rm B,f} \sim 2 - 10^4$。我们的结果与伽玛暴的弱磁化重子喷流模型一致。

英文摘要:

We use a parent sample of 118 gamma-ray burst (GRB) afterglows, with known redshift and host galaxy extinction, to separate afterglows with and without signatures of dominant reverse-shock emission and to determine which physical conditions lead to a prominent reverse-shock emission. We identify 10 GRBs with reverse shock signatures - GRBs 990123, 021004, 021211, 060908, 061126, 080319B, 081007, 090102, 090424 and 130427A. By modeling their optical afterglows with reverse and forward shock analytic light curves and using Monte Carlo simulations, we estimate the parameter space of the physical quantities describing the ejecta and circumburst medium. We find that physical properties cover a wide parameter space and do not seem to cluster around any preferential values. Comparing the rest-frame optical, X-ray and high-energy properties of the larger sample of non-RS-dominated GRBs, we show that the early-time ($<$ 1ks) optical spectral luminosity, X-ray afterglow luminosity and $γ$-ray energy output of our reverse-shock dominated sample do not differ significantly from the general population at early times. However, the GRBs with dominant reverse shock emission have fainter than average optical forward-shock emission at late time ($>$ 10 ks). We find that GRBs with an identifiable reverse shock component show high magnetization parameter $R_{\mathrm{B}} = \varepsilon_{\rm B,r}/\varepsilon_{\rm B,f} \sim 2 - 10^4$. Our results are in agreement with the mildly magnetized baryonic jet model of GRBs.

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