Hi, everyone,
I posted this to the HEN list, also.
Aql X-1 is in outburst. It should be up at the beginning of the night almost everywhere in the world right now, since it's equatorial.
This is a neutron star X-ray binary with an orbital period of just under 19 hours. It outbursts several times per year, so it's not particularly new, but there are some hints from 20 years ago that it has superhumps in its outburst light curve. The problem is that with the outburst durations of a few weeks, and a period of just under a day, it's hard to really nail down the outbursting period and prove that it's not just the orbital period. The VSNet folks seem to be taking data, so we should have data points from Japan. It would be great to get data from both the East and West of the Americas and from Europe and/or Africa so that the data will be well-sampled, despite the source only being up at the beginning of the night.
The reason that the superhumps are so potentially important here is that the donor star is probably relatively mass, because it's a subgiant. If it has superhumps, then the mass ratio should be less than 1/3, so that would mean that the neutron star would likely be more than 2 solar masses, which is interesting because not many of these heavy neutron stars have been found so far.
Right now, it's at R of about 17.5, but it should get 1-1.5 magnitudes brighter if the outburst is a normal outburst rather than a minioutburst.