K2 Extracted Lightcurves ("K2SFF")

The lightcurves from K2 contain larger systematics than the original Kepler mission, due to the reduction in pointing precision as a result of having to rely on only two reaction wheels. Vanderburg & Johnson have created a technique to correct for the pointing-dependent nature of the pixel-level fluxes. This correction improves the photometric precision by typical factors of 2-5, and results in median photometric performance of K2 targets to within a factor of two of the original, 4-wheeled mission. The team have released their extracted lightcurves (using a variety of photometric apertures), as well as diagnostic plots, for each target. The FITS lightcurves include all data points (with flags to indicate thruster firing), as well as multiple versions (each FITS extension is an extracted lightcurve for a different aperture). There are a total of twenty apertures provided: ten circular and ten based on the pixel response function. The final extension contains the summed image from all the postage stamp frames.