Where is V2492Cyg????
In the past we have repeatedly shown and discussed the light curve of V2492Cyg. For example the post from week 332 shows the full HOYS data set of the star until about two years ago. In the plot above we have shown the I-Band data for the star for the last about three years.
While in the past the object was briefly even brighter than 12mag, it now seems to not reach 16mag for most of the time. It is usually even fainter than about 19mag, which seems to be our detection limit in this filter. This is actually ‘normal’ for this object and the bright episodes as a few year back are rare.
How can the source change so much? Extinction (mostly)! While brightness outbursts due to mass accretion rate changes in young stars can reach a factor of 100 or so (5-6mag), these are very rare and occur on long timescales (FU-Ori outbursts). Changes by more than that, and there are hints that the object can be as faint as 22mag or fainter, can only be achieved by piling up sufficient material along the line of sight. This seems to be what is happening in this object. Large amounts of material are along the sight line and every now and again we receive a larger amount of light through a ‘hole’ in the disk material. We know that the source also changes it’s mass accretion rate, so often changes are caused by a combination of effects.
However, the brightening phases are impressive. If one zooms into the data, one finds that several of these brightness increases by about 3mag (factor of 15!) occur over one week. Intriguing!