GRB 201015A, 貌似看到了射电的移动?

GRB 201015A, 貌似看到了射电的移动?

 arXiv:2205.12750 [pdf, other]

VLBI observations of GRB 201015A, a relatively faint GRB with a hint of Very High Energy gamma-ray emission

S. Giarratana, L. Rhodes, B. Marcote, R. Fender, G. Ghirlanda, M. Giroletti, L. Nava, J. M. Paredes, M. E. Ravasio, M. Ribo, M. Patel, J. Rastinejad, G. Schroeder, W. Fong, B. P. Gompertz, A. J. Levan, P. O'Brien

Comments: Accepted for publication in Astronomy & Astrophysics, 11 pages, 3 figures

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

GRB 201015A is a long-duration Gamma-Ray Burst (GRB) which was detected at very high energies (> 100 GeV) using the MAGIC telescopes. If confirmed, this would be the fifth and least luminous GRB ever detected at this energies. We performed a radio follow-up of GRB 201015A over twelve different epochs, from 1.4 to 117 days post-burst, with the Karl G. Jansky Very Large Array, e-MERLIN and the European VLBI Network. We included optical and X-rays observations, performed with the Multiple Mirror Telescope and the Chandra X-ray Observatory respectively, together with publicly available data. We detected a point-like transient, consistent with the position of GRB 201015A until 23 and 47 days post-burst at 1.5 and 5 GHz, respectively. The source was detected also in both optical (1.4 and 2.2 days post-burst) and X-ray (8.4 and 13.6 days post-burst) observations. The multi-wavelength afterglow light curves can be explained with the standard model for a GRB seen on-axis, which expands and decelerates into a medium with a homogeneous density, while a circumburst medium with a wind-like profile is disfavoured. Notwithstanding the high resolution provided by the VLBI, we could not pinpoint any expansion or centroid displacement of the outflow. If the GRB is seen at the viewing angle which maximises the apparent velocity, we estimate that the Lorentz factor for the possible proper motion is Γα < 40 in right ascension and Γδ < 61 in declination. On the other hand, if the GRB is seen on-axis, the size of the afterglow is <5 pc and <16 pc at 25 and 47 days. Finally, the early peak in the optical light curve suggests the presence of a reverse shock component before 0.01 days from the burst.

来源： https://arxiv.org/list/astro-ph/new

用VLBI看的, 有下面这个关键词

射电的各时间用各望远镜看到的位置

可惜最开始看到的用e-MERLIN的精度不高. 不然如果都是毫角秒的量级, 说不定确实可以确定伽马暴喷流的移动了.

比较奇怪的是EVN的精度都是亚毫角秒了, 为什么25天和47天的位置都一样呢?

这个暴之所以引人关注, 主要是MAGIC也看到了, 有高能VHE的光子.

多波段的数据也有. 

其中红色是光学波段的, 在第三条竖线那里是超新星成分. 不过这个下降非常陡啊, 超新星没这么陡吧? (他们的虚线也是超新星简单拟合, 没有这么陡)

来自为知笔记(Wiz)