This week we have a timely look at the new Gaia alert source Gaia24ala. It has been flagged up as it showed a 1mag dimming event over a short amount of time. This was on top of a longer term (2yr) slow dimming over the same amount. Thus, the source was detected as about 2mag dimmer than its historical magnitude.

In the plot above we show the available HOYS data in the V, R, and I-band filters over the past 15 months. The object is situated in the NGC2268 (or M78) field, and thus is not observable for large amounts of time. However, we can see that the rapid dimming event only lasted about 50 days and the brightness dropped by almost 2mag. It will be interesting too see if this continues, or if the source remains dim/returns back to its original brightness.

The general behaviour of this star is fully in line of what we expect from a young stellar object. Short term variability of up to one magnitude. The deeper dimming events, though only seen once in this source so far, also regularly occur on such stars. They are usually caused by material in the disk moving into the line of sight to the central source during its orbital motion. The statistical behaviour of these events (i.e. how many are there, how often do they occur, how deep are they, how long do they last) can tell us about the small scale structure of the material in the disks. This is one of our ongoing research projects – so you will hear more on this from time to time 🙂