This week we have another look at one of the background objects in one of our HOYS fields. We found this one by looking at the images of the IC1396A – the Elephant Trunk Nebula – region. The star stands out as a very red source about two arcminutes from the very bright central star in the HII region.
The star in question is known as IRAS 21371+5716 and has been classified as a Carbon star. These are typically asymptotic giant branch stars who have more carbon than oxygen in their atmospheres. Like almost all giant stars these objects tend to be variable.
We show the I-Band light curve of the object in the plot above. It shows variations with amplitudes of up to two magnitudes. The period of the variations is about 550days. The peaks and troughs change their height by up to one magnitude. Longer term observations are needed to see if this is a secondary, even longer term, periodic pattern that determines the height of the maxima, or if the changes are stochastic. We shall look back at the source in a few years (few periods) to investigate.