This week we have a look back at an ‘old friend’ of the HOYS project, the unusual variable V2492Cyg. It has featured a few times as light curve of the week and we have even written an Astronomers Telegram about it back in 2017.
The object is situated in the Pelican nebula region, and the Gaia parallax even puts it slightly into the foreground of the main cluster at a distance of about 620pc, which is roughly 250pc closer than the main IC5070 region. The star shows very large variability in all filters on a number of timescales. The changes in brightness seem to be caused by a combination of changing mass accretion rate, and thus intrinsic luminosity changes, as well as variable line of sight extinction. This combination causes large changes of more then 8mag in the brightness.
In 2017, the source reached it’s brightest state observed so far. After that it varied by 3-4mag just below this maximum brightness for the next two years. By mid 2019 it dimmed significantly and vanished from view in all but the deepest of the HOYS I-Band images. It was then completely undetected for half a year in any of our images.
The latest HOYS data now shows that its brightness has recovered with vengeance. In the last 100 days it has increased it’s brightness in the I-Band by at least 5mag – a factor of 100 – but most likely by significantly more. For ‘normal’ young stars such an outburst would be widely reported and followed up, but not so for this source (at least I could not find any reports on it since 2017). The object does this all the time. It will be interesting to see what happens next. It has already lost a magnitude (factor 2-3) in the last 10 days since it reached the peak.