The largest ground-based catalogue of M-dwarf flares

ABSTRACT We present the largest ground-based catalogue of M-dwarf flares to date, comprising 1229 time-resolved events identified from the Zwicky Transient Facility (ZTF) data release 17. Using high-cadence ZTF observations collected between 2018 April and 2020 September, we analysed over 93 million variable light-curves containing 4.1 billion photometric measurements. Flare candidates were initially identified through a machine-learning pipeline trained on simulated flare light-curves, generated by injecting TESS-based flare templates into ZTF observational data. The candidates were then processed through an extensive post-filtering pipeline combining a machine-learning classifier, additional metadata gathering, and human inspection. For 655 flares with reliable Gaia-based distance estimates and well-sampled light-curve profiles, 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 the subset of 680 flaring stars with known vertical distances from the Galactic plane z, we estimated how the fraction of flaring stars varies with Galactic height and found a negative trend, indicating that the likelihood of flare activity decreases with increasing $|z|$. The resulting catalogue represents the most comprehensive ground-based sample of M-dwarf flares available 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.