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26-08-2021
Apertif and LOFAR uncover a Fast Radio Burst
| Submitter: | Inés Pastor-Marazuela, Liam Connor, Joeri van Leeuwen, Yogesh Maan, Sander ter Veen et al. |
| Description: | Today Nature publishes the paper "Chromatic periodic activity down to 120 MHz in a Fast Radio Burst". Apertif (left) and LOFAR (right) play leading roles for this result. Fast radio bursts (FRBs) are extragalactic astrophysical transients whose brightness requires emitters that are highly energetic, yet compact enough to produce the short, millisecond-duration bursts. FRBs had thus far been detected between 300 MHz and 8 GHz, but lower-frequency emission has remained elusive. A subset of FRBs is known to repeat, and one of those sources, FRB 20180916B, does so with a 16.3 day activity period. Using simultaneous radio data spanning the wide range of wavelengths covered by LOFAR plus Apertif, we show in this paper that FRB 20180916B emits down to 120 MHz. We also show its activity window is frequency dependent (that is, "chromatic"). Unexpectedly, we first saw 2 days of Apertif radio bursts (left), followed by 3 days of LOFAR radio bursts (right), in the 16-day cycle. So, the activity window is both narrower and earlier at higher frequencies. Binary wind interaction models predict a narrower periodic activity window at lower frequencies, which is the opposite of our observations. Our detections establish that low-frequency FRB emission can escape the local medium. For bursts of the same fluence, FRB 20180916B is more active below 200 MHz than at 1.4 GHz! Our chromatic results strongly disfavour scenarios in which absorption from strong stellar winds causes FRB periodicity. We demonstrate that some FRBs live in clean environments that do not absorb or scatter low-frequency radiation. For further reading, check out the journal paper, the free preprint or the Dutch press release. |
| Copyright: | JvL |
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