This week we look at the HOYS data from last winter of the variable young star V397 Ori, which is situated in the Orion Nebula. It was flagged as a variable source (Gaia19dnm) a few years ago, when it underwent a 1.5year long, 1.5mag deep dimming event. The 2MASS image reveals that the source has a nearby companion, about 6.6 arcseconds apart. However, the Gaia parallaxes indicate that the two stars do not form a binary. The companion is about 22pc closer than the variable shown here.
The light curve looks like a mess. In the roughly 6 months of data shown, the brightness in all filters seems to vary randomly by about 1.5mag in all filters. However, if one zooms into the data it becomes apparent that the star more or less periodically changes its brightness with the amplitude of 1.5mag periodically, roughly every 5.5days. The minimum magnitude after each period is slightly different each time. So the source could be an AA-Tau type object with a warped inner disk, or it has quite variable hot spots that change their properties on timescales shorter than the rotation period.
We are in the process of identifying and analysing all periodic variables in all fields. It will be interesting to see how this source will be characterised (AA-Tau or hot spot) when this work is concluded. I will let you know when the results are in…..