We have a look at a light curve from the Lambda-Ori target region this week. This field, which is centred on the cluster also known as Collinder 69, or MWSC 0580, is one of the lesser observed targets that we have – probably because it is not as pretty as the other fields, i.e. it looks a bit boring. However, it is the most northerly field in the Orion constellation on our list. Hence it is visible for a much longer time for the northern hemisphere observers, than all the other fields in Orion. But yes, the Moon is moving through it every 4 weeks – which is not helping :-).
We now have 10 years of data for this field, and show one of the light curves above. The object has no special name, but most commonly it is known as 2MASS J05351974+0947476. We can see that for the first 6 years of data, the object doesn’t change much. There is some short term random variation, which to some extend is the noise in the data, but nothing exciting is happening.
In the last 4 years the source has dimmed by about 0.1mag and the short term scatter in the data has increased to the same level (i.e. 10 percent). If one zooms in, one finds that the short term variations are correlated between the filters, thus these are real fluctuations in the brightness. As mentioned previously, it is the long tern nature of HOYS that allows us to identify objects that do change their behaviour over time….