Just over a year ago we looked at the light curve of the star TT-Ori, which was announced as the Gaia alert object Gaia22ehy. So it is time to check in with the object again to see what has happened. Within 10 months of the alert the Gaia photometry shows a drop of almost 2.5mag. This minimum occurred roughly in August this year. Since then it has brightened again by almost 1.2mag.

Our HOYS data covers the general dimming and brightening very well, with the obvious gap of about 90 days in the summer, when the object is not observable. In the plot above we show the B, V, R, and I-band data we have since the start of the current observing season for this target in Orion. We can see the general increase in brightness like in Gaia. Note that the Gaia magnitudes very roughly correspond to our R-Band data.

On top of the general brightening we also see short time scale fluctuations of up to one magnitude within about a week or so. The B-band data is available for all days when we have observations in the other filters. However, this example nicely shows how the detection limits influence the data. One can see that as soon as the source gets fainter than about 15.2 mag in the V-band, it is not detectable in the B-band data anymore. Thus, if one analysis the variability of sources near the detection limit in one of the filters, one needs to be aware that missing data can alter the perception of the type of variability the source has. In this case, if one looks at just the part with B data available, one could think the source shows outbursts from time to time. However, in the other filters we see that the dimming events are just missing in the B-data and that the light curve varies symmetrically around some (slowly changing) mean brightness.