Stellar flares detected with the Next Generation Transit Survey

TL;DR

This paper reports the detection and analysis of 610 stellar flares from 339 stars using NGTS data, revealing differences in flare activity across spectral types and stellar ages.

Contribution

It introduces a generalized method for measuring stellar flare rates accounting for detection sensitivity variations and provides new insights into flare activity across different stellar populations.

Findings

K and early M stars have similar flare rates at field age.

Fully convective M stars show increased white-light flaring activity.

Pre-main sequence K and M stars exhibit higher flare activity than main sequence stars.

Abstract

We present the results of a search for stellar flares in the first data release from the Next Generation Transit Survey (NGTS). We have found 610 flares from 339 stars, with spectral types between F8 and M6, the majority of which belong to the Galactic thin disc. We have used the 13 second cadence NGTS lightcurves to measure flare properties such as the flare amplitude, duration and bolometric energy. We have measured the average flare occurrence rates of K and early to mid M stars and present a generalised method to measure these rates while accounting for changing detection sensitivities. We find that field age K and early M stars show similar flare behaviour, while fully convective M stars exhibit increased white-light flaring activity, which we attribute to their increased spin down time. We have also studied the average flare rates of pre-main sequence K and M stars, showing they exhibit increased flare activity relative to their main sequence counterparts.