This week we look at a variable star in one of our additional target fields, centred on Gaia alert objects. In this case it is the field around Gaia16agv, which is also known as YY Ori. This field is situated just south of the Orion Nebula and most young stars in the field are hence part of that cluster, or at least at the same distance (400pc) as the majority of the other young objects in that area.

The Gaia light curve of the star shows that it varies by about one magnitude, but has no other long term trends. If one zooms into the Gaia data, one can see that on some occasions the full one magnitude variations occur in less than one day. This agrees with the classification of the object as an Orion type variable star.

We show about three months of HOYS data from last winter in the image above. It displays the same kind of behaviour with variations of up to one magnitude on very short timescales. Indeed, it looks like noise. However, since the variations are similar in the three filters, it is clear that these changes are real.

This light curve is also an excellent example of the success of the HOYS project, in terms of the collaboration of participants. This is one of the fields that we usually do not observe with our Beacon Observatory. Instead, when one looks at were the data points are coming from, then one finds a nice mix of many of our participants who have added the target to their regular schedule. Thus, despite it’s very southern location and the usually bad weather in winter for most of our observers, they have achieved a coverage in most filters roughly every two nights. This is vital to characterise these kind of fast, stochastically variable sources. Thank you to everyone who helps with gathering these data.