Winter is coming and hence our targets from the ‘Winter’ list are starting to be observable. While this is not yet very evident for the Northern hemisphere observers, the Orion targets in particular have been easily visible in the morning sky in the Southern hemisphere for well over a month now.
This week’s light curve is showing the data for AA Ori, the last group of data points are the new observations from late July and August. Compared to the earlier data from the winter of 2022/23, the object has “calmed down” a bit. The plot shown above does not really do the object justice and we highly recommend exploring the light curve in detail at http://astro.kent.ac.uk/HOYS-CAPS/lightcurve/ . Just type the object name into the search box (AA Ori), select ‘Name’, press ‘Search’ and then click on the result page to open the plot. Try zooming in on certain parts of the data to see the detailed behaviour.
The source is very interesting as over time it changes its behaviour. We have discussed it in several previous posts: week 228, week 167, week 144, and week 103. Have a look back at these posts to see how at different times the source behaved differently. It can be randomly varying, showing stochastic deep dimming events, periodic dimming events and almost sinusoidal periodic variability (with a different period than the periodic dimming). This means we can study very many different aspects of the source at different times. Apologies for using the word different 5 times in three sentences, plus one time in this one ;-). A new final year undergraduate project will aim this year to find a way to identify such ever changing objects. If we find more of them, we will let you know.