Thanks to our data processing volunteers we have now fully cleared our data input backlog, and only a handful of recently uploaded images remain to be processed. There are now more than 86,600 images in our database and in excess of 320 million brightness measurements.  This allows us to look at some light curves of variable stars again, with all the recently added data. We are also making good progress on restoring the full dataset.

This week we are looking at the variable star V555Ori, which is situated north of the Orion Nebula (M42). However, it is far enough away from the M42 field, that it has it’s own HOYS target field. This is centred in the smaller nebulosity, next to M42. We only show the I-band data in the plot above. There are also B, V, and R-band data, but for large parts of the shown time period the source is too faint to be detected in these filters.

The light curve looks very noisy at first glance. However, all the variability you see is real. The measurement uncertainties on all data points are less than 0.2mag, while the source changes its brightness by up to 2.5mag over the duration of the shown light curve. If you look carefully, there are changes of one magnitude from one day to the next in some cases. Thus, this is a nice case of an extremely fast and larger amplitude variable. Changes are probably caused by accretion rate changes, which can occur very fast, but there might be a component of line of sight extinction changes, which can explain the longer term dimming and recovery – though this needs detailed analysis. This is a good project for an undergraduate student to find out what is going on ….. 🙂