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28th of October 2019
ASKAP observations of a flaring X-ray binary, MAXI J1535–571
by Chauhan et al.
On 2 September 2017, an uncatalogued X-ray binary system was discovered by both the Monitor of All-sky X-ray Image (MAXI) and the Neil Gehrels Swift Observatory, and designated MAXI J1535–571. Multi-wavelength studies of the system strongly suggest that the accreting compact object is a stellar-mass black hole. However, the physical parameters, including the black hole mass and distance, and the peak luminosity of the outburst were still uncertain. Chauhan et al. used the ASKAP Early Science array of 12 antennas to monitor the MAXI J1535–571 over seven epochs from 21 September to 2 October 2017. The radio flare accompanying the X-ray outburst was bright enough that the team could study the HI absorption spectrum from gas clouds along the line-of-sight and thereby constrain the distance to the source.

The image above shows the 1.34 GHz light curve of MAXI J1535–571 from 21 September to 2 October 2017. Two distinct peaks were observed, on 21 and 23 September, reaching flux densities > 450 mJy, most likely corresponding to separate flaring events. The radio flux density then steadily declined, reaching a level of ∼20 mJy by 2 October. More details are given in the paper, published in Monthly Notices of the Royal Astronomical Society.




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