We are showing light curves from the Kepler 2-wheel mission for Campaign 0 (a.k.a. “K2 C-0”) now and wanted to explain some issues that you may notice with these data. The K2 C-0 data are poorer quality than what you are used to seeing. The Kepler team is still working optimize the light curves, and this has been made more difficult by instabilities in the pointing control of the spacecraft. You can expect to see more trends and glitches. Furthermore, the first few weeks of K2 C-0 data were not useable so the length of the light curve (in days) is shorter than what you might have expected. All of this should improve for the next campaign, C-1.
A second issue with the K2 C-0 data is that we don’t have access to information about the stars. We know the EPIC numbers, coordinates, brightness of the stars, and the program numbers (telling us who requested observation of the stars). Postdoctoral Fellow Ji Wang has been an enormous help – he wrote a program to filter the published 2MASS and Sloan catalogs and to search for stars within a small radius about the EPIC coordinates. Ji then used the stellar brightness to obtain an unambiguous identification. This helps, but we still don’t know the stellar gravities (radii), masses or spectral types. Therefore, the information we can display for each of the K2 C-0 stars is much more limited than what you are used to seeing.
Since we don’t know the stellar radii, we are not able to make up accurate simulations for the K2 C0 data. To compensate we will show these light curves to more people than usual to build up consensus about the presence of transits.
The K2 data have many more selection effects than the original Kepler data because the targets are drawn from several guest observer programs. However, this is part of the fun – scavenger hunting for planets among the K2 stars is sure to be an adventure!
We are also trying to improve our turn-around time for PH results. Instead of waiting until we obtain telescope time to carry out follow-up data and publish a paper (sometimes a year later!) we will put the high probability transit candidates that you identify on the “Planet Hunters Object of Interest” (or PHOI – which I think is pronounced something like “fooey”). This is supposed to be a fun home-grown analog of the “Kepler Objects of Interest.”
Thanks to Andrew Vanderburg at Harvard University who has extracted these K2 C-0 light curves for Planet Hunters.