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arXiv 1210.7252astro-ph.HEastro-ph.CO
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短GRB120323A瞬发中光球成分的证据及其对GRB硬度-亮度关系的影响

Evidence for a Photospheric Component in the Prompt Emission of the Short GRB120323A and its Effects on the GRB Hardness-Luminosity Relation

S. Guiriec, F. Daigne, R. Hascoët, G. Vianello, R. Mochkovitch, F. Ryde, C. Kouveliotou, S. Xiong, P. N. Bhat, S. Foley, D. Grüber, J. M. Burgess, S. McGlynn, J… 展开作者

S. Guiriec, F. Daigne, R. Hascoët, G. Vianello, R. Mochkovitch, F. Ryde, C. Kouveliotou, S. Xiong, P. N. Bhat, S. Foley, D. Grüber, J. M. Burgess, S. McGlynn, J. McEnery, N. Gehrels

摘要:

短GRB 120323A具有费米/GBM探测到的最高通量。在这里,我们研究其显着的光谱特性和它们的演变使用两个光谱模型:(i)一个单一的发射组件的情况下,光谱是由经验带函数建模,和(ii)一个两个组件的情况下,热(类普朗克)发射同时观察到的非热组件(带函数)。我们发现,后者模型拟合的综合爆发谱显着优于前者,并且它们各自的光谱参数是显着不同的:当只与带函数拟合时,事件的Epeak是异常软的短GRB,而添加热分量导致更典型的短GRB值。我们的时间分辨光谱分析产生了类似的结果。我们认为双组分模型是GRB 120323A的首选解释,基于:(i)双组分方案的能带函数参数的值和演变,这对于短GRB更典型,以及(ii)当我们采用双组分模型拟合时,在数据中出现了显着的硬度-强度相关性,通常在GRB中发现;在仅限频带的拟合中不存在相关性。GRB 110721 A是一个长时间爆发,具有强烈的光球辐射,表现出完全相同的行为。我们的结论是,GRB 120323A有很强的光球辐射贡献,第一次在短GRB观察到。磁耗散模型很难与这些结果相一致,相反,这些结果有利于光球热发射和快速冷却的内部冲击同步辐射。最后,我们利用一个更大的伽玛暴集合L,i =(1.59 +/-0.84 <$.10^50(Epeak,i)^(1.33 +/-0.07)erg/s),在源坐标系中导出了一个可能具有普适性的硬度-光度关系,它可以作为宇宙学中可能的红移估计量。

英文摘要:

The short GRB 120323A had the highest flux ever detected with the Fermi/GBM. Here we study its remarkable spectral properties and their evolution using two spectral models: (i) a single emission component scenario, where the spectrum is modeled by the empirical Band function, and (ii) a two component scenario, where thermal (Planck-like) emission is observed simultaneously with a non-thermal component (a Band function). We find that the latter model fits the integrated burst spectrum significantly better than the former, and that their respective spectral parameters are dramatically different: when fit with a Band function only, the Epeak of the event is unusually soft for a short GRB, while adding a thermal component leads to more typical short GRB values. Our time-resolved spectral analysis produces similar results. We argue here that the two-component model is the preferred interpretation for GRB 120323A, based on: (i) the values and evolution of the Band function parameters of the two component scenario, which are more typical for a short GRB, and (ii) the appearance in the data of a significant hardness-intensity correlation, commonly found in GRBs, when we employee two-component model fits; the correlation is non-existent in the Band-only fits. GRB 110721A, a long burst with an intense photospheric emission, exhibits the exact same behavior. We conclude that GRB 120323A has a strong photospheric emission contribution, first time observed in a short GRB. Magnetic dissipation models are difficult to reconcile with these results, which instead favor photospheric thermal emission and fast cooling synchrotron radiation from internal shocks. Finally, we derive a possibly universal hardness-luminosity relation in the source frame using a larger set of GRBs L,i=(1.59+/-0.84).10^50 (Epeak,i)^(1.33+/-0.07) erg/s), which could be used as a possible redshift estimator for cosmology.

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