Artist's impression of a magnetar. (Sophia Dagnello, NRAO/AUI/NSF)

The first star to send fast radio bursts from inside the Milky Way is sending it again. The star, Magnetar SGR 1935+2154, emitted the fast radio burst in April and has flared up again, this is another chance for astronomers to solve more than one important cosmic mystery.

The CHIME/FRB collaboration observed SGR 1935+2154 emitting three millisecond radio bursts in three seconds on 8 October 2020. After the CHIME/FRB observation, the FAST radio telescope discovered that something else – a pulsed radio emission correlating with the magnetar’s spin period.

“It’s really exciting to see SGR 1935+2154 back again, and I’m optimistic that as we study these bursts more carefully, it will help us better understand the potential relationship between magnetars and fast radio bursts,” astronomer Deborah Good of the University of British Columbia in Canada, and member of the CHIME/FRB said.

Due to the fact that many fast radio burst sources appear to erupt once and have not been observed repeating, they are exceptionally uncertain.

Additionally, the ones that have been observed mostly come from so far away, the telescopes could not pick out individual stars. Both of these traits make FRBs difficult to track down either to a precise source galaxy, or a known cause.

However SGR 1935+2154 is just about 30,000 light-years away.

As soon as the power of the signal was revised for distance, FRB 200428 was discovered to be not quite as powerful as extragalactic fast radio bursts.

“If the same signal came from a nearby galaxy, like one of the nearby typical FRB galaxies, it would look like an FRB to us,” astronomer Shrinivas Kulkarni of Caltech told ScienceAlert in May.

“Something like this has never been seen before.”

“Although less bright than the detection earlier this year, these are still very bright bursts which we’d see if they were extragalactic,” Good said.

“One of the most interesting aspects of this detection is that our three bursts seem to have occurred within one rotation period. The magnetar is known to rotate once every ~3.24 seconds, but our first and second bursts were separated by 0.954 seconds, and the second and third were separated by 1.949 seconds. That’s a bit unusual, and I think it’s something that we’ll be looking into further going forward.”

That could disclose something different and beneficial about magnetar behaviour.

Obviously, astronomers have discovered the origin of the first intra-galactic FRB to be of serious concern. When CHIME/FRB announced their detection, other astronomers reached out to have a glimpse at the star, comprising a team led by Zhu Weiwei of the National Astronomical Observatories of China who had access to FAST, the vastest single-aperture radio telescope in the world.
And they discovered something interesting, also noted in The Astronomer’s Telegram – pulsed radio emission.

Initially this year, Australian astronomers pointed out a magnetar that was acting like a radio pulsar – this might be the “missing link” between the two, and proof that some magnetars could grow into pulsars. SGR 1935+2154 could be another piece of the puzzle.

“Based on these results and the increasing bursting activities, we speculate that the magnetar may be in the process of turning into an active radio pulsar,” Weiwei’s team wrote.
What an absolutely bloody fascinating little star this is turning out to be.


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