Our work on investigating the variability of spots on young stars is continuing. This week we have a look at a pre-view plot from this work, which we are writing up as a paper in the near future. The star in question is known as number 2066866222797779072 in the 3rd data release from Gaia. It is a member of the Pelican Nebula star forming region.
We have established that the star shows periodic variations and the period is 1.4616d. The amplitudes of the the variability have then been measured every three months, and are shown in the top panel of the graph. Only V (green), R (red), and I (black) data have been analysed. The x-axis doe not show time, but the number of the 3-months period investigated, ending in autumn last year (slice 34). You can hence count-back the years, 4 data points per year, along the graph. The amplitude in all filters has slightly increased over the first four years of our data. In the last two years, it has slightly decreased again. There are no clear indications of appearing and disappearing spots. These would potentially manifest as periods of large amplitudes, intertwined with phases of lower, non-measurable amplitudes.
In the bottom graph we show the phase of the light curve minimum. While there are some short time-scale variations, they are most likely caused by measurement uncertainties. However, there is a long term trend with the position in phase changing from about zero degrees to 120 degrees over the six years. This could mean that the spot is slowly moving across the surface of the star in longitude. I.e. at a pace of about 20 degrees per year. More likely is that we have determined a slightly wrong period. If the latter is correct, then we can work out by how much out period is wrong. This corresponds to about 28s, or 0.0002d. Hence, the period should be changed by this amount for our analysis.