Exoplanets & Stellar Populations Group

A PSF-based approach to Kepler/K2

Libralato et al. (2016) MNRAS, 456, 1137

Kepler and K2 data analysis reported in the literature is mostly based on aperture photometry. Because of Kepler's large, undersampled pixels and the presence of nearby sources, aperture photometry is not always the ideal way to obtain high-precision photometry and, because of this, the data set has not been fully exploited so far.
We present a new method (Libralato et al., 2016 MNRAS, 456, 1137) that builds on our experience with undersampled HST images. The method involves a point-spread function (PSF) neighbour subtraction and was specifically developed to exploit the huge potential offered by the K2 "super-stamps" covering the core of dense star clusters, but our technique is perfectly suitable to also analyse sparse fields imaged in single, isolated stamps.
By using a high-angular-resolution catalogue and PSFs we are able to pinpoint each star in the adopted input catalogue into each Kepler/K2 exposure and to measure its flux after all detectable close-by neighbours are subtracted from the image. This PSF-based technique allows us to (i) increase the number of analysable objects in the field, (ii) estimate an unbiased flux for a given source, (iii) extract the light curve of a star in a crowded environment and (iv) improve the photometric precision reachable for faint stars.
We are currently working on different stellar clusters imaged during K2 Campaigns and Kepler main mission.

Related papers to Kepler/K2 data analysis:

• Paper I: Libralato et al. (2016) MNRAS, 456, 1137: Detailed description of the method.
• Paper II: Libralato et al. (2016) MNRAS, 463, 1780: Exoplanet candidates in Praesepe (M 44)
• Paper III: Nardiello et al. (2016) MNRAS, 463, 1831: Variable stars and exoplanet candidates in M 67

In the table below, together with all light curves (6-th column), we release other useful material such as input catalogs, variable and exoplanet-candidate catalogs, stacked images. All files can be found in each channel folder (7-th column).

	Due to the large number of the files stored, we warn the Users that the redirect may take a few moments. "Don't abandon all hope, ye who enter here!" (semicit.)

Mission	Campaign	Cluster ID	Module	Channel	Electronic material		Papers	Readme file
K2	0	M 35 + NGC 2158	24	81	LCs	All files	Paper I	Readme.txt
K2	5	M 44	14 (*)	45	LCs	All files	Paper II	Readme.txt
				46	LCs	All files
				47	LCs	All files
				48	LCs	All files
		M 67	6	13	LCs	All files	Paper III	Readme.txt
				14	LCs	All files

^(*) Note that for M 44 the input and the variable/exoplanet catalogs in each Module-14 channel folder are the same. We copied them into each channel folder for sake of completeness.