The largest ground-based catalogue of M-dwarf flares

TL;DR

This paper presents the largest ground-based catalogue of M-dwarf flares, analyzing over a billion measurements to identify and characterize 1,229 flare events, revealing correlations with spectral subtype and Galactic height.

Contribution

It introduces a machine-learning pipeline for flare detection in large-scale survey data and provides a comprehensive catalogue with detailed flare properties and statistical analyses.

Findings

Flare energies range from 10^31 to 10^35 erg.

Flaring fraction decreases with Galactic height.

Flare frequency increases towards later M spectral types.

Abstract

We present the largest ground-based catalogue of M-dwarf flares to date, comprising 1,229 time-resolved events identified in Zwicky Transient Facility Data Release 17. Using high-cadence ZTF observations collected between April 2018 and September 2020, we analyzed over 93 million variable light curves containing 4.1 billion photometric measurements. Flare candidates were identified through a machine-learning pipeline trained on simulated light curves generated by injecting TESS-based flare templates into ZTF data and then refined through an extensive post-filtering stage combining an additional classifier, metadata checks, and human inspection. For 655 flares with reliable Gaia-based distances and well-sampled light curves, we derived bolometric energies ranging from 10^31 to 10^35 erg. A clear correlation is observed between flare frequency and spectral subtype, with a sharp increase toward later M dwarfs, particularly near M4-M5, coinciding with the transition to full convection. Using 680 flaring stars with known vertical distances from the Galactic plane, we find that the fraction of flaring stars decreases with increasing Galactic height. The resulting catalogue provides the most comprehensive ground-based sample of M-dwarf flares and establishes a framework for flare detection and classification in upcoming wide-field surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time.