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arXiv 1207.6399astro-ph.HEastro-ph.CO
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对来自伽马射线暴的瞬发、分散无线电脉冲的限制

Limits on prompt, dispersed radio pulses from gamma-ray bursts

Keith W. Bannister, Tara Murphy, Bryan M. Gaensler, John E. Reynolds

摘要:

我们用12米望远镜在1.4 GHz频率上搜索了9个伽马射线暴(GRB)的瞬发射电辐射,时间分辨率为64 μ s ~ 1 s。我们在两次伽玛暴后的几分钟内探测到了单次色散射电脉冲,其强度大于6 σ。这两个脉冲的色散测量值都远远超过了预期的银河值,并且隐含的速率与已知的单个色散脉冲源不相容。这两个脉冲的到达时间也与GRB X射线光变曲线中的突变相吻合。空试验和统计参数排除了随机波动作为这些脉冲的起源,置信度分别为>95%和97%,尽管一个简单的人口参数支持伽玛射线暴起源的置信度只有2%。我们警告说,我们不能排除RFI作为这些脉冲的起源。如果单个脉冲与伽玛暴无关,我们将伽玛暴后200 ~ 1800 s之间发射的射电脉冲通量密度设为上限1.27 w^{-1/2} Jy,其中64 us < w < 32 ms为脉冲宽度。我们为长时间尺度(>1 s)变化设定了小于760 Jy的限制。这些限制是伽玛射线暴现象早期阶段在高时间分辨率和GHz频率下最具约束力的限制。

英文摘要:

We have searched for prompt radio emission from nine Gamma Ray Bursts (GRBs) with a 12 m telescope at 1.4 GHz, with a time resolution of 64 us to 1 s. We detected single dispersed radio pulses with significances >6 sigma in the few minutes following two GRBs. The dispersion measures of both pulses are well in excess of the expected Galactic values, and the implied rate is incompatible with known sources of single dispersed pulses. The arrival times of both pulses also coincide with breaks in the GRB X-ray light curves. A null trial and statistical arguments rule out random fluctuations as the origin of these pulses with >95% and 97% confidence, respectively, although a simple population argument supports a GRB origin with confidence of only 2%. We caution that we cannot rule out RFI as the origin of these pulses. If the single pulses are not related to the GRBs we set an upper limit on the flux density of radio pulses emitted between 200 to 1800 s after a GRB of 1.27 w^{-1/2} Jy, where 64 us < w < 32 ms is the pulse width. We set a limit of less than 760 Jy for long timescale (>1 s) variations. These limits are some of the most constraining at high time resolution and GHz frequencies in the early stages of the GRB phenomenon.

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