arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1902.01779astro-ph.HE
收藏

对FRB 121102的低频频谱的约束

Constraints on the low frequency spectrum of FRB 121102

L. J. M. Houben, L. G. Spitler, S. ter Veen, J. P. Rachen, H. Falcke, M. Kramer

摘要:

虽然重复的快速射电暴(FRB)的数量仍然很少,但它们为后续观测提供了一个独特的机会,可以增强我们对它们的来源以及整个FRB种群的潜在知识。获得更多的爆发光谱可以更好地理解这些明亮的毫秒级射电脉冲的起源。因此,我们进行了$\sim$ 20小时的同时观察FRB 121102与Effelsberg 100米射电望远镜和低频阵列(LOFAR),以限制从FRB 121102在1.4 GHz和150 MHz的爆发的光谱行为。这一活动导致在1.4千兆赫检测到9个新的突发,但没有与LOFAR同时检测。假设两个频率处的注量之比按幂律缩放,我们将$α$ > -1.2 $\pm$ 0.4的下限置于FRB 121102的瞬时宽带发射的注量的光谱指数上。对于该限值的推导,LOFAR的实际通量检测阈值是根据经验确定的,假设爆发将如NE 2001模型所预测的那样散射。在L波段的脉冲串重复率R中观察到显著的变化。在2016年9月的观察期间,检测到9次爆发,得出R = 1.1 $\pm$ 0.4 hr $^{-1}$,而在11月没有检测到爆发,得出R < 0.3 hr $^{-1}$(95%置信限)。这一变化与FRB 121102早期的幕式发射相一致。在盲法和靶向搜索中,在150 MHz下使用LOFAR未发现爆发,导致R < 0.16 hr $^{-1}$的重复率限值(95%置信限)。突发重复率比FRB 121102在3,2,1.4,和0.15 GHz的不确定性内是一致的,其频谱低于1 GHz的平坦化。

英文摘要:

While repeating fast radio bursts (FRBs) remain scarce in number, they provide a unique opportunity for follow-up observations that enhance our knowledge of their sources and potentially of the FRB population as a whole. Attaining more burst spectra could lead to a better understanding of the origin of these bright, millisecond-duration radio pulses. We therefore performed $\sim$20 hr of simultaneous observations on FRB 121102 with the Effelsberg 100-m radio telescope and the Low Frequency Array (LOFAR) to constrain the spectral behaviour of bursts from FRB 121102 at 1.4 GHz and 150 MHz. This campaign resulted in the detection of nine new bursts at 1.4 GHz but no simultaneous detections with LOFAR. Assuming that the ratio of the fluence at two frequencies scales as a power law, we placed a lower limit of $α$ > -1.2 $\pm$ 0.4 on the spectral index for the fluence of the instantaneous broad band emission of FRB 121102. For the derivation of this limit, a realistic fluence detection threshold for LOFAR was determined empirically assuming a burst would be scattered as predicted by the NE2001 model. A significant variation was observed in the burst repeat rate R at L-band. During observations in September 2016, nine bursts were detected, giving R = 1.1 $\pm$ 0.4 hr$^{-1}$, while in November no bursts were detected, yielding R < 0.3 hr$^{-1}$ (95% confidence limit). This variation is consistent with earlier seen episodic emission of FRB 121102. In a blind and targeted search, no bursts were found with LOFAR at 150 MHz, resulting in a repeat rate limit of R < 0.16 hr$^{-1}$ (95% confidence limit). Burst repeat rate ratios of FRB 121102 at 3, 2, 1.4, and 0.15 GHz are consistent within the uncertainties with a flattening of its spectrum below 1 GHz.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑