A Late-time Radio Survey of Short Gamma-ray Bursts at z < 0.5: New Constraints on the Remnants of Neutron-star Mergers
A Late-time Radio Survey of Short Gamma-ray Bursts at z < 0.5: New Constraints on the Remnants of Neutron-star Mergers
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DOI：
10.3847/1538-4357/abb407
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发表时间：
2020-06
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影响因子：
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通讯作者：
G. Schroeder;B. Margalit;W. Fong;B. Metzger;P. Williams;K. Paterson;K. Alexander;T. Laskar;A. Goyal;E. Berger
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文献类型：
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作者：
G. Schroeder;B. Margalit;W. Fong;B. Metzger;P. Williams;K. Paterson;K. Alexander;T. Laskar;A. Goyal;E. Berger
双星中子星(BNS)合并产生的巨大的、快速旋转的磁星残骸可能会将它们的一小部分能量沉积到周围的千里诺瓦抛射物中，为来自抛射物与环爆介质相互作用的同步无线电信号提供动力。在这里，我们提供了9个低红移短伽马射线暴(GRB；z<；0.5)的6.0GHz甚大阵列(VLA)观测，这些爆发发生后的静止帧时间尺度为≈2.4-13.9年。我们对爆发位置的Fν≲6-20μJy或Lν≲(0.6-8.3)×10 2 8erg S−1 Hz−1的射电连续谱辐射设置了3个≲限制。将这些限制与适当考虑相对论效应的新的光曲线模型相比较，得到了0.03M⊙(0.1M⊙)抛射质量下E EJ≲(0.6-6.7)×10 52erg(Erg)射电连续辐射的能量限制。我们对27个观测频率为5.5-6.0 GHz的短伽玛暴进行了统一的再分析，发现≳有50%的短伽玛暴在合并过程中没有形成稳定的磁星残留物。假设短伽玛暴是由来自银河系BNS人群的BNS合并加上一小部分类似GW194025的高质量合并产生的，我们对非自转中子星的最大质量(NS；托尔曼-奥本海默-沃尔科夫质量；M tov)施加限制，发现f GW190425=0.4；这个限制随着f GW190425的增大而增加。在诸如VLA天空调查(VLASS)等非目标调查中发现(或缺乏)无线电残留物，可能会对产生稳定残留物的合并的比例产生更严格的限制。如果在Vlass发现无线电残留物，这表明就其产生的残留物的稳定性而言，短伽玛暴是BN合并的偏向群体。
Massive, rapidly spinning magnetar remnants produced as a result of binary neutron-star (BNS) mergers may deposit a fraction of their energy into the surrounding kilonova ejecta, powering a synchrotron radio signal from the interaction of the ejecta with the circumburst medium. Here, we present 6.0 GHz Very Large Array (VLA) observations of nine, low-redshift short gamma-ray bursts (GRBs; z < 0.5) on rest-frame timescales of ≈2.4–13.9 yr following the bursts. We place 3σ limits on radio continuum emission of F ν ≲ 6–20 μJy at the burst positions, or L ν ≲ (0.6–8.3) × 1028 erg s−1 Hz−1. Comparing these limits with new light-curve modeling that properly incorporates relativistic effects, we obtain limits on the energy deposited into the ejecta of E ej ≲ (0.6–6.7) × 1052 erg ( erg) for an ejecta mass of 0.03 M ⊙ (0.1 M ⊙). We present a uniform reanalysis of 27 short GRBs with 5.5–6.0 GHz observations, and find that ≳50% of short GRBs did not form stable magnetar remnants in their mergers. Assuming short GRBs are produced by BNS mergers drawn from the Galactic BNS population plus an additional component of high-mass GW194025-like mergers in a fraction f GW190425 of cases, we place constraints on the maximum mass of a nonrotating neutron star (NS; Tolman–Oppenheimer–Volkoff mass; M TOV), finding for f GW190425 = 0.4; this limit increases for larger values of f GW190425. The detection (or lack thereof) of radio remnants in untargeted surveys such as the VLA Sky Survey (VLASS) could provide more stringent constraints on the fraction of mergers that produce stable remnants. If radio remnants are discovered in VLASS, this suggests that short GRBs are a biased population of BNS mergers in terms of the stability of the remnants they produce.