# An update to the EVEREST K2 pipeline: Short cadence, saturated stars, and Kepler-like photometry down to Kp = 15

## TL;DR

The EVEREST 2.0 pipeline significantly enhances K2 photometric data quality by improving de-trending methods, including saturated and faint stars, achieving near-Kepler precision across a wide magnitude range, and is adaptable to other surveys.

## Contribution

This paper introduces a new regularization scheme for pixel level decorrelation that includes neighboring stars and handles saturated stars, improving photometric precision over previous versions.

## Key findings

- 10-20% higher photometric precision than previous EVEREST versions
- Recover Kepler-like precision up to Kp=14 and Kp=15 for certain campaigns
- De-trended all short cadence targets with improved accuracy

## Abstract

We present an update to the EVEREST K2 pipeline that addresses various limitations in the previous version and improves the photometric precision of the de-trended light curves. We develop a fast regularization scheme for third order pixel level decorrelation (PLD) and adapt the algorithm to include the PLD vectors of neighboring stars to enhance the predictive power of the model and minimize overfitting, particularly for faint stars. We also modify PLD to work for saturated stars and improve its performance on extremely variable stars. On average, EVEREST 2.0 light curves have 10-20% higher photometric precision than those in the previous version, yielding the highest precision light curves at all Kp magnitudes of any publicly available K2 catalog. For most K2 campaigns, we recover the original Kepler precision to at least Kp = 14, and to at least Kp = 15 for campaigns 1, 5, and 6. We also de-trend all short cadence targets observed by K2, obtaining even higher photometric precision for these stars. All light curves for campaigns 0-8 are available online in the EVEREST catalog, which will be continuously updated with future campaigns. EVEREST 2.0 is open source and is coded in a general framework that can be applied to other photometric surveys, including Kepler and the upcoming TESS mission.