Automated Extended Aperture Photometry of K2 variable stars

TL;DR

This paper introduces autoEAP, an automated open-source pipeline for extended aperture photometry of K2 variable stars, addressing systematics caused by the spacecraft's two-wheel operation and improving light curve quality.

Contribution

The paper presents a novel automated pipeline, autoEAP, that extends aperture photometry for K2 data and includes a new detrending method for periodic variables.

Findings

autoEAP produces improved light curves compared to other methods

The new detrending method effectively removes long-term instrumental signals

Application to high-amplitude variables demonstrates its effectiveness

Abstract

Proper photometric data are challenging to obtain in the K2 mission of the Kepler space telescope due to strong systematics caused by the two-wheel-mode operation. It is especially true for variable stars wherein physical phenomena occur on timescales similar to the instrumental signals. We originally developed a method with the aim to extend the photometric aperture to be able to compensate the motion of the telescope which we named Extended Aperture Photometry (EAP). Here we present the outline of the automatized version of the EAP method, an open-source pipeline called autoEAP. We compare the light curve products to other photometric solutions for examples chosen from high-amplitude variable stars. Besides the photometry, we developed a new detrending method, which is based on phase dispersion minimization and is able to eliminate long-term instrumental signals for periodic variable stars.