This week we look at some progress we are making on the analysis of rotation periods. The last time we looked at this was in week 285, where we had a preliminary list of rotation periods. We have now manually curated this list to ensure no dubious periods remain. If you wish to compare the two plots, you will find that many points are in exactly the same places, but a few have vanished or have been added. The plot shows the rotation period on the x-axis and the K-W2 colour on the y-axis. If this colour is above 0.5mag, then the sources are thought to have (a disk of) hot dust close to the star.
This time, we colour code the objects based on the star forming region they are in. The legend gives you the names. There are a few red dots, which are sources outside any of the listed regions. Also: ‘Orion’ refers to all objects in the Orion star forming, except if they are in the field around sigma-Ori. We can see from the distribution that the naive picture of young stars starting with longer rotation periods while possessing a inner disk, then loosing this disk and spinning up due to angular momentum conservation, does not full hold. There are a few objects that have detected hot dust but are rotating fast, and there is a sizable fraction (about one quarter) that rotates slowly without an inner dust disk.
We are now finalising the fitting of the spot properties (determining their sizes and temperatures). Then we will finish investigating if there are any differences of these spot properties based on the rotation period and or the presence of an inner dust disk….