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arXiv 2008.10822astro-ph.HE
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磁星巨耀斑起源于GRB 200415 A:瞬时GeV发射,时间分辨的$\rm E_p~ -~L_{iso}$相关性和意义

Magnetar Giant Flare Originated GRB 200415A: Transient GeV emission, Time-Resolved $\rm E_p~ -~L_{iso}$ Correlation, and Implications

Vikas Chand, Jagdish C. Joshi, Rahul Gupta, Yu-Han Yang, Dimple, Vidushi Sharma, Jun Yang, Manoneeta Chakraborty, Jin-Hang Zou, Lang Shao, Yi-Si Yang, Bin-Bin Z… 展开作者

Vikas Chand, Jagdish C. Joshi, Rahul Gupta, Yu-Han Yang, Dimple, Vidushi Sharma, Jun Yang, Manoneeta Chakraborty, Jin-Hang Zou, Lang Shao, Yi-Si Yang, Bin-Bin Zhang, S. B. Pandey, Ankush Banerjee, Eman Moneer

摘要:

巨耀斑(GF)是软伽马射线中继器(SGR)发出的不寻常的爆发,它在几分之一秒内释放出巨大的能量。这些SGR-GF或GF候选物的余辉发射是辨别其组成、相对论速度和发射机制的非常有益的手段。GRB 200415 A是最近发现的GF候选者,其观测方向与附近的玉夫座星系一致,速度为3.5 Mpc。在这项工作中,我们寻找瞬态伽玛射线辐射在过去的观测费米-LAT在GRB 200415 A的方向。这些观测结果证实了GRB 200415 A仅被观测到一次GeV的瞬态源。一个纯粹的对等离子体火球不能提供所需的能量的解释GeV余辉发射和重子穷人外流另外需要解释余辉发射。一个重子丰富的外流也是可行的,因为它可以解释的可变性和观察到的准热光谱的即时排放,如果耗散是通过内部冲击发生在光球层以下。利用时间分辨瞬发光谱的峰值能量($E_p$)及其通量($F_p$),我们发现了GRB 200415 A的$E_p$与$F_p$或$E_p$与各向同性光度$L_{\rm iso}$之间的相关性。这支持了SGRs-GF中发现的$E_p$ - $E_{\rm iso}$相关性的内在本质,因此有利于重子贫流出。我们的研究结果还表明,在工作过程中的初始尖峰不同的机制,并在此流出的即时发射光谱特性的演变将本质上是由于注入过程。

英文摘要:

Giant flares (GFs) are unusual bursts from soft gamma-ray repeaters (SGRs) that release an enormous amount of energy in a fraction of a second. The afterglow emission of these SGR-GFs or GF candidates is a highly beneficial means of discerning their composition, relativistic speed, and emission mechanisms. GRB 200415A is a recent GF candidate observed in a direction coincident with the nearby Sculptor galaxy at 3.5 Mpc. In this work, we searched for transient gamma-ray emission in past observations by Fermi-LAT in the direction of GRB 200415A. These observations confirm that GRB 200415A is observed as a transient GeV source only once. A pure pair-plasma fireball cannot provide the required energy for the interpretation of GeV afterglow emission and a baryonic poor outflow is additionally needed to explain the afterglow emission. A baryonic rich outflow is also viable, as it can explain the variability and observed quasi-thermal spectrum of the prompt emission if dissipation is happening below the photosphere via internal shocks. Using the peak energy ($E_p$) of the time-resolved prompt emission spectra and their fluxes ($F_p$), we found correlation between $E_p$ and $F_p$ or $E_p$ and isotropic luminosity $L_{\rm iso}$ for GRB 200415A. This supports the intrinsic nature of $E_p$-$E_{\rm iso}$ correlation found in SGRs-GFs, hence favoring a baryonic poor outflow. Our results also indicate a different mechanism at work during the initial spike, and that the evolution of the prompt emission spectral properties in this outflow would be intrinsically due to the injection process.

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