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LOFAR Detection of 110–188 MHz Emission and Frequency-dependent Activity from FRB 20180916B
The Astrophysical Journal Letters ( IF 8.8 ) Pub Date : 2021-04-09 , DOI: 10.3847/2041-8213/abec72
Z. Pleunis 1, 2 , D. Michilli 1, 2 , C. G. Bassa 3 , J. W. T. Hessels 3, 4 , A. Naidu 5 , B. C. Andersen 1, 2 , P. Chawla 1, 2 , E. Fonseca 1, 2, 6, 7 , A. Gopinath 3, 4 , V. M. Kaspi 1, 2 , V. I. Kondratiev 3, 8 , D. Z. Li 9, 10 , M. Bhardwaj 1, 2 , P. J. Boyle 1, 2 , C. Brar 1, 2 , T. Cassanelli 11, 12 , Y. Gupta 13 , A. Josephy 1, 2 , R. Karuppusamy 14 , A. Keimpema 15 , F. Kirsten 16 , C. Leung 17, 18 , B. Marcote 15 , K. W. Masui 17, 18 , R. Mckinven 11, 12 , B. W. Meyers 19 , C. Ng 11 , K. Nimmo 3, 4 , Z. Paragi 15 , M. Rahman 11, 20 , P. Scholz 11 , K. Shin 17, 18 , K. M. Smith 21 , I. H. Stairs 19 , S. P. Tendulkar 13, 22
Affiliation  

The object FRB 20180916B is a well-studied repeating fast radio burst source. Its proximity (∼150 Mpc), along with detailed studies of the bursts, has revealed many clues about its nature, including a 16.3 day periodicity in its activity. Here we report on the detection of 18 bursts using LOFAR at 110–188 MHz, by far the lowest-frequency detections of any FRB to date. Some bursts are seen down to the lowest observed frequency of 110 MHz, suggesting that their spectra extend even lower. These observations provide an order-of-magnitude stronger constraint on the optical depth due to free–free absorption in the source’s local environment. The absence of circular polarization and nearly flat polarization angle curves are consistent with burst properties seen at 300–1700 MHz. Compared with higher frequencies, the larger burst widths (∼40–160 ms at 150 MHz) and lower linear polarization fractions are likely due to scattering. We find ∼2–3 rad m−2 variations in the Faraday rotation measure that may be correlated with the activity cycle of the source. We compare the LOFAR burst arrival times to those of 38 previously published and 22 newly detected bursts from the uGMRT (200–450 MHz) and CHIME/FRB (400–800 MHz). Simultaneous observations show five CHIME/FRB bursts when no emission is detected by LOFAR. We find that the burst activity is systematically delayed toward lower frequencies by about 3 days from 600 to 150 MHz. We discuss these results in the context of a model in which FRB 20180916B is an interacting binary system featuring a neutron star and high-mass stellar companion.



中文翻译:

来自 FRB 20180916B 的 110–188 MHz 发射和频率相关活动的 LOFAR 检测

物体 FRB 20180916B 是一个经过充分研究的重复快速射电暴源。它的接近度(~150 Mpc)以及对爆发的详细研究揭示了许多关于其性质的线索,包括其活动周期为 16.3 天。在这里,我们报告了在 110-188 MHz 下使用 LOFAR 检测 18 个突发,这是迄今为止所有 FRB 的最低频率检测。可以看到一些爆发下降到 110 MHz 的最低观察频率,这表明它们的频谱延伸得更低。由于光源局部环境中的自由吸收,这些观察结果对光学深度提供了一个数量级的更强约束。没有圆极化和几乎平坦的极化角曲线与在 300-1700 MHz 处看到的突发特性一致。与更高的频率相比,较大的突发宽度(约 40–160 ms 在 150 MHz)和较低的线性极化分数可能是由于散射造成的。我们发现~2-3 rad m-2法拉第旋转测量的变化可能与源的活动周期相关。我们将 LOFAR 突发到达时间与来自 uGMRT(200-450 MHz)和 CHIME/FRB(400-800 MHz)的 38 个先前发布的突发和 22 个新检测到的突发进行比较。当 LOFAR 没有检测到发射时,同时观测显示了五个 CHIME/FRB 爆发。我们发现,从 600 到 150 MHz,突发活动向较低频率系统地延迟了大约 3 天。我们在一个模型的背景下讨论这些结果,其中 FRB 20180916B 是一个相互作用的双星系统,具有中子星和大质量恒星伴星。

更新日期:2021-04-09
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