This week’s featured light curve is not a young star. Instead we are looking at the Mira type variable, KS Cyg.  These type of stars are pulsating giants with periods of hundreds of days and large amplitudes. They are also very red in colour, i.e. much brighter at longer wavelength.

We show here the V-Band light curve of KS Cyg. The star is situated in our less well observed target field of MWSC3274, hence we do not have a huge amount of data yet. According to the ASAS-SN data, the object has a period of about 296days. This is also evident in our data.

The V-Band data is the only one where we can follow the behaviour of the star throughout its period. In the B-Band the star usually gets too faint during the minima. In R and I the star is too bright and saturates the images during the maxima. We can also see, as is typical for these objects, that the amplitudes of the star vary in height, and reach at least 5mag in V. Note that this is a factor of 100 in brightness!

A closer look at the increasing part of the light curve reveals a ‘hump’. These are real and are most likely resonances between the fundamental and first overtone vibration mode of these stars.