LONG-DURATION RADIO TRANSIENTS LACKING OPTICAL COUNTERPARTS ARE POSSIBLY GALACTIC NEUTRON STARS
LONG-DURATION RADIO TRANSIENTS LACKING OPTICAL COUNTERPARTS ARE POSSIBLY GALACTIC NEUTRON STARS
复制标题
缺乏光学对应物的长持续时间无线电瞬变可能是银河中子星
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
E. Waxman
中科院分区：
文献类型：
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作者：
E. Ofek;B. Breslauer;B. Breslauer;A. Gal;D. Frail;M. Kasliwal;S. Kulkarni;E. Waxman
最近，鲍尔和合作者检测到了一类新的5 GHz频段的无线电瞬变，持续时间为数小时到数天，缺乏任何可见光对应物。我们提出了新的深近红外（IR）观测包含这些瞬变的字段，并没有找到对应的限制幅度K = 20.4马格。我们认为，明亮的（>1焦耳）无线电瞬变最近报道的Kida等人。是一致的，是鲍尔等人的额外的例子。瞬变。我们把这些事件称为“长时间无线电瞬变”。这个星群的主要特征是：时间尺度长于30分钟但短于几天;非常大的速率，103 deg−2 yr−1;祖先的天空表面密度>60 deg−2（95%置信度）在银河系纬度<$40 °; 1.4-5 GHz光谱斜率，fν να，α <$0;最明显的是，在静止状态下，没有任何X射线、可见光、近红外和无线电对应物。我们讨论了可能与这些瞬变有关的假定的已知天体，并排除了与许多类型的天体的关联，包括超新星、伽马射线暴、类星体、类星体和M-矮星耀斑。星系褐矮星或星系际介质中的某种奇异爆炸仍然是合理的（尽管是推测性的）选择。我们认为，这些无线电瞬变的一个有吸引力的祖先候选人是银河系孤立的老中子星（NS）类。我们面对这一假设与Monte Carlo模拟的空间分布的老NS，并找到令人满意的协议的大面密度。此外，缺乏安静的对应物是很自然的解释。在这个框架中，我们发现：在鲍尔等人的事件的平均距离。样本是kpc的顺序，典型的距离Kida等人。瞬变被限制在45 pc和2 kpc之间（在95%的置信水平），这些事件应该重复的时间尺度为几个月的顺序，和sub-mJy级爆发应该表现出银河系的纬度依赖性。我们讨论了引起所观察到的射电发射的两种可能机制：非相干同步辐射和相干发射。我们推测，如果后者是正确的，长时间的无线电瞬变是溅射古老的恒星或磁星，并将表现出脉冲发射。
Recently, a new class of radio transients in the 5 GHz band and with durations of the order of hours to days, lacking any visible-light counterparts, was detected by Bower and collaborators. We present new deep near-infrared (IR) observations of the field containing these transients, and find no counterparts down to a limiting magnitude of K = 20.4 mag. We argue that the bright (>1 Jy) radio transients recently reported by Kida et al. are consistent with being additional examples of the Bower et al. transients. We refer to these groups of events as “long-duration radio transients.” The main characteristics of this population are: timescales longer than 30 minutes but shorter than several days; very large rate, ∼103 deg−2 yr−1; progenitor's sky surface density of >60 deg−2 (at 95% confidence) at Galactic latitude ∼40°; 1.4–5 GHz spectral slopes, fν ∝ να, with α ≳ 0; and most notably the lack of any X-ray, visible-light, near-IR, and radio counterparts in quiescence. We discuss putative known astrophysical objects that may be related to these transients and rule out an association with many types of objects including supernovae, gamma-ray bursts, quasars, pulsars, and M-dwarf flare stars. Galactic brown dwarfs or some sort of exotic explosions in the intergalactic medium remain plausible (though speculative) options. We argue that an attractive progenitor candidate for these radio transients is the class of Galactic isolated old neutron stars (NSs). We confront this hypothesis with Monte Carlo simulations of the space distribution of old NSs, and find satisfactory agreement for the large areal density. Furthermore, the lack of quiescent counterparts is explained quite naturally. In this framework, we find: the mean distance to events in the Bower et al. sample is of order kpc; the typical distance to the Kida et al. transients are constrained to be between 45 pc and 2 kpc (at the 95% confidence level); these events should repeat with a timescale of order several months; and sub-mJy level bursts should exhibit Galactic latitude dependence. We discuss two possible mechanisms giving rise to the observed radio emission: incoherent synchrotron emission and coherent emission. We speculate that if the latter is correct, the long-duration radio transients are sputtering ancient pulsars or magnetars and will exhibit pulsed emission.