The Broadband Counterpart of the Short GRB 200522A at z = 0.5536: A Luminous Kilonova or a Collimated Outflow with a Reverse Shock?
The Broadband Counterpart of the Short GRB 200522A at z = 0.5536: A Luminous Kilonova or a Collimated Outflow with a Reverse Shock?
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DOI：
10.3847/1538-4357/abc74a
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发表时间：
2020-08
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通讯作者：
W. Fong;T. Laskar;J. Rastinejad;A. R. Escorial;G. Schroeder;J. Barnes;C. Kilpatrick;K. Paterson;E. Berger;B. Metzger;Y. Dong;A. Nugent;R. Strausbaugh;P. Blanchard;A. Goyal;A. Cucchiara;G. Terreran;K. D. Alexander;T. Eftekhari;Chris L. Fryer;B. Margalit;R. Margutti;M. Nicholl
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作者：
W. Fong;T. Laskar;J. Rastinejad;A. R. Escorial;G. Schroeder;J. Barnes;C. Kilpatrick;K. Paterson;E. Berger;B. Metzger;Y. Dong;A. Nugent;R. Strausbaugh;P. Blanchard;A. Goyal;A. Cucchiara;G. Terreran;K. D. Alexander;T. Eftekhari;Chris L. Fryer;B. Margalit;R. Margutti;M. Nicholl
我们提出的射电余辉和近红外（NIR）对应的斯威夫特短伽玛射线暴（GRB）GRB 200522 A，位于一个小的投影偏移量为10.1千秒差距的年轻，恒星形成的宿主星系在z = 0.5536的中心的发现。余辉的射电和X射线光度与轴上宇宙学短伽玛暴一致。我们的哈勃太空望远镜在2.3天的静止帧时间观测到的近红外对应物的光度为1.3 × 1042 erg s−1。这是大大低于轴上短伽玛射线暴余辉检测，但是一个108 -17倍，比GW 170817的kilonova更明亮，显着比任何kilonova候选人，可比的观测存在更明亮。对应物的颜色（i − y = −0.08 ± 0.21;静止坐标系）和光度的组合不能单独用标准的放射性加热来解释。我们提出了两种方案来解释GRB 200522 A的宽带行为：一个同步加速器前向冲击与发光kilonova（可能由磁星能量沉积推动），或正向和反向冲击从一个14°，相对论（Γ0 <$10）喷流。包括增强的放射性加热速率、低镧系元素质量分数或来自后期中央发动机活动的额外加热源的组合的模型可以提供可行的替代解释。如果GRB 200522 A中确实产生了稳定的磁星，我们预测，在爆发后的10.3 -6年，可以检测到晚期射电辐射，其沉积能量为1053 erg。与GRB 200522 A类似光度的引力波事件的对应物将在目前的光学搜索中探测到250 Mpc。
We present the discovery of the radio afterglow and near-infrared (NIR) counterpart of the Swift short gamma-ray burst (GRB) GRB 200522A, located at a small projected offset of ≈1 kpc from the center of a young, star-forming host galaxy at z = 0.5536. The radio and X-ray luminosities of the afterglow are consistent with those of on-axis cosmological short GRBs. The NIR counterpart, revealed by our Hubble Space Telescope observations at a rest-frame time of ≈2.3 days, has a luminosity of ≈(1.3–1.7) × 1042 erg s−1. This is substantially lower than on-axis short GRB afterglow detections but is a factor of ≈8–17 more luminous than the kilonova of GW170817 and significantly more luminous than any kilonova candidate for which comparable observations exist. The combination of the counterpart’s color (i − y = −0.08 ± 0.21; rest frame) and luminosity cannot be explained by standard radioactive heating alone. We present two scenarios to interpret the broadband behavior of GRB 200522A: a synchrotron forward shock with a luminous kilonova (potentially boosted by magnetar energy deposition), or forward and reverse shocks from a ≈14°, relativistic (Γ0 ≳ 10) jet. Models that include a combination of enhanced radioactive heating rates, low-lanthanide mass fractions, or additional sources of heating from late-time central engine activity may provide viable alternate explanations. If a stable magnetar was indeed produced in GRB 200522A, we predict that late-time radio emission will be detectable starting ≈0.3–6 yr after the burst for a deposited energy of ≈1053 erg. Counterparts of similar luminosity to GRB 200522A associated with gravitational wave events will be detectable with current optical searches to ≈250 Mpc.