Abstract
ABSTRACT We present the results of a search for stellar flares from stars neighbouring the target sources in the Kepler short cadence data. These flares have been discarded as contaminants in previous surveys and therefore provide an unexplored resource of flare events, in particular high-energy events from faint stars. We have measured M dwarf flare energies up to 1.5 × 1035 erg, pushing the limit for flare energies measured using Kepler data. We have used our sample to study the flaring activity of wide binaries, finding that the lower mass counterpart in a wide binary flares more often at a given energy. Of the 4430 flares detected in our original search, 298 came from a neighbouring star, a rate of 6.7 ± 0.4 per cent for the Kepler short cadence light curves. We have used our sample to estimate a 5.8 ± 0.1 per cent rate of false positive flare events in studies using Transiting Exoplanet Survey Satellite short cadence data.
Highlights
IntroductionAdditional light from neighbouring stars will dilute astrophysical signals from a target star of interest, or even introduce signals where there were none before
Blending of multiple stars within apertures is a known problem in astronomy
We identified that 515 flares in 26 Kepler short cadence lightcurves were either due to a nearby source, or due to there being flares from both the target star and a close companion
Summary
Additional light from neighbouring stars will dilute astrophysical signals from a target star of interest, or even introduce signals where there were none before. A noted example of this is in exoplanet transit searches, where a deep signal from a faint eclipsing binary within a photometric aperture is diluted by the brighter target star, resulting in an apparent transit signal. False positive signals such as this, if not fully understood, can impact large scale statistical studies, such as the incidence of stars hosting a transiting planet. Measuring the position of the centroid, the centre of light, during the transit can identify a neighbouring star as the true source which can be flagged for removal (e.g Bryson et al 2013; Günther et al 2017)
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