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Mon Jun 08, 2020

Observing outburst onset in a low-mass X-ray binary

SAX J1808.4—3658 is the first accretion-powered millisecond pulsar ever discovered, and still one of the best-studied, thanks to a quasi-regular series of outbursts since 1996. Based on the regularity of the outbursts, I'd predicted that it would return to activity in 2019 May. This prediction was a bit off, as it turned out, since we didn't hear a peep out of it until late July in the same year. Even so, thanks to the prediction and a series of optical and X-ray observations led by Monash PhD student Adelle Goodwin, we gathered data giving a view of the outburst onset of unprecedented detail.

Adelle presented her work at the 236th AAS meeting last week, and also took part in a press event the same day. Our press release got picked up and distributed widely, at space.com, Science Daily,, phys.org,, CNET and even Nine news. Adelle also appeared on RRR's Einstein-a-go-go show and was interviewed by a number of other outlets.

On the science side, the unexpectedly long delay of 12d between the optical and X-ray activity may have implications for the most widely-accepted model which explains how these outbursts are triggered. Adelle's paper on the study has been submitted to MNRAS.

And the next outburst? You'll have to wait until 2023 November — or perhaps even later.

Read the paper arXiv:2006.02872

Labels: 2020, /pulsars