This week we look at a star in the Pelican Nebula field. However, it is not a young star, but situated in the background. It has ‘one of those’ light curves, that see on first glance noisy or random. However, if one zooms in, one finds that the variations in brightness (up to almost one magnitude) occur in all filters at the same time. This means they are real and not noise in the data.
Still, when looking at the pattern in the above light curve, they seem random. Sometimes there are several days without change, sometimes there are very short dimming events and sometimes they seem to last 2 days. This is caused by the cadence of the observations. Indeed, this is an eclipsing binary with a period of 1d 4h 14m 25s. It has primary and secondary eclipses that are almost the same depth, and thus a dimming event occurs roughly every 14hr, but our typical cadence is 24hr.
You can see the regularity only if you phase-fold the data with the correct period. We did show this about 5yr ago in week 88 of this feature. The data in the above plot is a zoom into the lightcurve for observations about 2yr ago. The pattern has obviously not changed 🙂 .