The Galactic M Dwarf Flare Rate

TL;DR

This paper develops a statistical model to predict the flare rates of M dwarfs in the Galaxy, considering survey parameters and stellar populations, to better understand their variability and impact on exoplanet habitability.

Contribution

The paper introduces a comprehensive model of M dwarf flare rates that incorporates new observational data and accounts for inactive stars, improving predictions of stellar variability in surveys.

Findings

Enhanced flare rate predictions for M dwarfs across the Galaxy.

Quantified the impact of inactive stars on flare occurrence.

Provided observational constraints on flare frequency distributions.

Abstract

M dwarfs are known to flare on timescales from minutes to hours, with flux increases of several magnitudes in the blue/near-UV. These frequent, powerful events, which are caused by magnetic reconnection, will have a strong observational signature in large, time-domain surveys. The radiation and particle fluxes from flares may also exert a significant influence on the atmospheres of orbiting planets, and affect their habitability. We present a statistical model of flaring M dwarfs in the Galaxy that allows us to predict the observed flare rate along a given line of sight for a particular survey depth and cadence. The parameters that enter the model are the Galactic structure, the distribution of magnetically active and inactive M dwarfs, and the flare frequency distribution (FFD) of both populations. The FFD is a function of spectral type, activity, and Galactic height. Although inactive M dwarfs make up the majority of stars in a magnitude-limited survey, the FFD of inactive stars is very poorly constrained. We have organized a flare monitoring campaign comprising hundreds of hours of new observations from both the ground and space to better constrain flare rates. Incorporating the new observations into our model provides more accurate predictions of stellar variability caused by flares on M dwarfs. We pay particular attention to the likelihood of flares appearing as optical transients (i.e., host star not seen in quiescent data).