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arXiv 2409.07686astro-ph.HE
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短伽马射线暴GRB 230217A的早期射电余辉

The early radio afterglow of short GRB 230217A

G. E. Anderson, G. Schroeder, A. J. van der Horst, L. Rhodes, A. Rowlinson, A. Bahramian, S. I. Chastain, B. P. Gompertz, P. J. Hancock, T. Laskar, J. K. Leung, R. A. M. J. Wijers

AI总结:

本研究报道短伽马射线暴GRB 230217A的早期射电余辉,通过ATCA和VLA在爆发后32分钟开始观测,获得迄今最早的射电探测,并利用亮温度论证对射电波段伽马射线暴施加了最高的最小洛伦兹因子约束,强调了快速射电后续观测的重要性。

摘要:

我们展示了短伽马射线暴(GRB)230217A的射电余辉,该余辉在伽马射线瞬时辐射后不到1天内被澳大利亚望远镜致密阵列(ATCA)和卡尔·G·扬西甚大阵列(VLA)探测到。ATCA快速响应系统在尼尔·盖雷斯·斯威夫特天文台探测到GRB 230217A后自动触发观测,并在爆发后仅32分钟开始以5.5和9 GHz频率观测该事件,持续7小时。将7小时的观测分为三个时间分箱图像,我们获得了爆发后对数中心时间分别为1、2.8和5.2小时的射电探测,其中第一个是迄今为止任何伽马射线暴最早的射电探测。光变曲线的下降与逆冲激波发射一致,前提是观测频带低于光谱峰值且不受同步自吸收影响。这使得GRB 230217A成为第五个在早期(爆发后<1天)射电探测归因于逆冲激波的短伽马射线暴。基于亮温度论证,我们利用早期射电探测对射电波段的伽马射线暴施加了最高的最小洛伦兹因子约束(Γ_min > 50,在约1小时时)。我们的结果证明了具有长积分时间和良好灵敏度的快速射电后续观测对于探测短伽马射线暴快速演化的射电辐射以及探测其逆冲激波的重要性。

英文摘要:

We present the radio afterglow of short gamma-ray burst (GRB) 230217A, which was detected less than 1 day after the gamma-ray prompt emission with the Australia Telescope Compact Array (ATCA) and the Karl G. Jansky Very Large Array (VLA). The ATCA rapid-response system automatically triggered an observation of GRB 230217A following its detection by the Neil Gehrels Swift Observatory and began observing the event just 32 minutes post-burst at 5.5 and 9 GHz for 7 hours. Dividing the 7-hour observation into three time-binned images allowed us to obtain radio detections with logarithmic central times of 1, 2.8 and 5.2 hours post-burst, the first of which represents the earliest radio detection of any GRB to date. The decline of the light curve is consistent with reverse shock emission if the observing bands are below the spectral peak and not affected by synchrotron self-absorption. This makes GRB 230217A the fifth short GRB with radio detections attributed to a reverse shock at early times ($<1$ day post-burst). Following brightness temperature arguments, we have used our early radio detections to place the highest minimum Lorentz factor ($Γ_{min} > 50$ at $\sim1$ hour) constraints on a GRB in the radio band. Our results demonstrate the importance of rapid radio follow-up observations with long integrations and good sensitivity for detecting the fast-evolving radio emission from short GRBs and probing their reverse shocks.

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