We mentioned before that a large fraction of the Gaia photometric alerts for young stars are situated in the HOYS target fields. This week we look at another alert published on February the 25th. The object is Gaia22atl, which is situated in the IC348 cluster in Perseus. This is a very red (and thus faint at short wavelengths) known young star. It is also known as 2MASS J03434517+320358 and situated just north-west of the famous HH211 protostellar outflow.
The very red colour of the source means it is quite faint at short wavelength. Thus, we only have sufficient data for a light curve analysis in the I-band. The object is of course detected at some times in shorter wavelengths filters, in particular when it is bright. But it then dims below the detection limit. Thus, we only show the I-band light curve in the above plot. As one can see the object is extremely variable. During the last seven years we have detected variations of four magnitudes in the I-band. All of which happen on very short timescales of weeks or shorter. The Gaia data similarly shows up to 5mag (a factor of 100 in flux) variations on similarly short timescales. The variability is most likely even larger, as the source gets too faint for detection at some times.
It is not clear what causes the variations. These are either changes in the accretion rate or the line of sight extinction. Colour measurements would help to identify the reason, but they are hard to obtain accurately, due to the faintness of the source at short wavelengths. However, this light curve is a very good example why brightness measurements of fainter stars with slightly larger uncertainties are still useful for some science analysis. A change in brightness of several magnitudes can easily be detected, even if the uncertainties are of the order of 0.2mag (20 percent of in flux).