This week we look back at an old friend of the project. The very variable star V2492Cyg. It is situated in the Pelican Nebula (IC5070) one of our most observed target regions, which is close the North America Nebula on the sky. Indeed both regions are physically connected and only separated by a dark clouds of gas and dust. The Pelican nebula is a particular active star forming region with several hundred young stars and has been the subject of some of our HOYS papers already.

The star varies by large amounts as can be seen in the V and I-band light curve. The range in the I-band is clearly above 7mag, i.e. more than a factor of 200. It can also vary by almost that on very short timescales of a few weeks – in both ways, getting fainter and brighter. The star had been bright for a few years at the start of our observations and then it had dimmed below our detection limit. The last time we looked at it, it had just re-emerged from invisibility. As one can see, it then quickly disappeared again and has again been mostly invisible. We will look at it again when it comes back above the detection limit.

The underlying physical reasons for the changes in brightness in this object are twofold. On one hand it changes it’s mass accretion rate, while on the other hand the amount of extinction from the surrounding circumstellar material also varies significantly. The combination of these two effects creates this ‘interesting’ light curve, but also makes it next to impossible to fully investigate all the details of the behaviour. In particular it becomes impossible to disentangle these two main reasons of variability from each other.