This week we have a look at the star V982Cep. It is situated in the field of NGC7129. With a most likely distance from Gaia of 734pc, the star is clearly a member of the young cluster. Looking at the spectral energy distribution, the object also shows excess emission at infra-red wavelengths. This is a clear sign of an accretion disk around the star.
In the literature the star is classified as an Orion variable. This means it shows random fluctuations in brightness at varying timescales. The HOYS light curve, displayed above does fully agree with this assessment. We show the V, R, and I broadband filters in the image (note the shifts of some of the filters for better visibility). Due to the circumpolar nature of the field, the four year long data has almost no larger gaps.
We see that there are long term fluctuations on timescales of about one year and one magnitude. Additionally there are shorter term fluctuations lasting up to a few months and half a magnitude in size. Then there are even shorter term changes in brightness with daily variations. Note that the error bars are plotted for all data points but are in most cases much smaller that the data point.
The purple points in the figure indicate the brightness measured in the Hydrogen alpha emission line. Stars that are brighter in Halpha than in R show strong Halpha emission lines which indicate strong ongoing mass accretion. As you can see, we have now Halpha data for three years of this field and can study the R-Halpha colours of stars and their variability. This will allow us to identify and characterise how stars change their accretion rate on time scales of several years.