A PSF-Based Approach To Kepler/K2 Data ("PSFK2")

The Kepler/K2 mission offered to the science community the opportunity of obtaining high-precision light curves for a large variety of stellar fields, including stellar clusters. However, most Kepler/K2 data analyses reported in the literature are based on aperture photometry. Aperture photometry is perfectly suitable to investigating stars in sparse fields but it suffers from severe limitations in crowded environments like the central regions of stellar clusters. Thus, the wealth of information included in stellar clusters analyzed with the Kepler/K2 mission is often unexplored. The team has made use of their experience with undersampled Hubble Space Telescope images and developed a new method to analyze crowded regions with the Kepler/K2 data. The combination of a high-angular-resolution catalog and accurate point-spread-function (PSF) models allows them to pinpoint a star in a Kepler/K2 exposure and measure its flux after all detectable nearby stars are PSF subtracted from the image. This PSF-based technique: (i) increases the number of analyzable objects in the field, (ii) provides an unbiased flux measurement for each source, (iii) extracts stellar light curves in a crowded environment and (iv) improves the reachable photometric precision for faint stars. This technique is designed to exploit the huge potential offered by the "super-stamps", but it is also perfectly suitable to analyze single, isolated stamps. The team releases the light curves for stars in the open clusters M35 and NGC2158 observed during Campaign 0, and M44 and M67 in Campaign 5. They also provide the high-angular-resolution input catalogs used in their works, the lists of the variable stars identified (only for M 44 and M67 clusters) and the Kepler/K2 stacked images for each cluster.