Phil Charles, a recently retired professional astronomer with an interest in X-ray transients and a long-time friend of mine, drew my attention to MAXI J1820+070 which is presently in outburst and has been for an unusually long time. Kevin Hills and Joan Genebriera have been providing me with photometry data. I’m about to buy Joan’s observatory in La Palma later this month, all being well.
The object is roughly 13th magnitude and is expected to vary by 0.2 magnitude with a period of somewhere between 2 and 8 hours, that being a plausible orbital period for a star in close orbit around a black hole. Present data is noisy and, because of the limited visibility of Ophiuchus at this time of year, is only for a couple of hours or so each night.
We would welcome more data to tie down the behaviour of these rather unusual objects. Please contact me for more information if you wish to join in. My role is to be the principal point of contact and to perform the initial analysis.
If you prefer email, I’m paul @ leyland . vispa . com