A detection threshold in the amplitude spectra calculated from Kepler data obtained during K2 mission

TL;DR

This paper revises the detection threshold for amplitude spectra in Kepler K2 data, establishing a more accurate threshold at 5.4 times the noise level for reliable pulsation detection, improving analysis accuracy.

Contribution

It introduces a revised detection threshold specific to Kepler K2 data, accounting for coverage and cadence variations, enhancing pulsation analysis accuracy.

Findings

Detection threshold at 5.4 times the noise level for 95% confidence

Threshold varies between 4.8 and 5.7 with cadence changes

Improves reliability of pre-whitening in space-based pulsation data

Abstract

We present our analysis of simulated data in order to derive a detection threshold which can be used in the pre-whitening process of amplitude spectra. In case of ground-based data of pulsating stars, this threshold is conventionally taken to be four times the mean noise level in an amplitude spectrum. This threshold is questionable when space-based data are analyzed. Our effort is aimed at revising this threshold in the case of continuous 90-day Kepler K2 phase observations. Our result clearly shows that a 95% confidence level, common for ground observations, can be reached at 5.4 times the mean noise level and is coverage dependent. In addition, this threshold varies between 4.8 and 5.7, if the number of cadences is changed. This conclusion should secure further pre-whitening and helps to avoid over-interpretation of spectra of pulsating stars observed with the Kepler spacecraft during K2 phase. We compare our results with the standard approach widely used in the literature.