ASASSN-18di: discovery of a $\Delta V \sim 10$ flare on a mid-M dwarf

TL;DR

This paper reports the discovery and analysis of a powerful white-light superflare on a mid-M dwarf star, estimated to have an energy of around 4.1×10^36 ergs, detected by the ASAS-SN survey.

Contribution

It presents the first detailed characterization of a superflare on a previously unknown M dwarf, including stellar parameters and flare energy estimation.

Findings

Detected a superflare with ΔV ~ 10 on an M dwarf.

Estimated flare energy to be approximately 4.1×10^36 ergs.

Determined the star's properties consistent with a mid-M dwarf at 2.2 kpc.

Abstract

We report and characterize a white-light superflare on a previously undiscovered M dwarf detected by the ASAS-SN survey. Employing various color-magnitude and color-spectral type relationships, we estimate several stellar parameters, including the quiescent V-band magnitude, from which we derive a flare amplitude of $\Delta V \sim 10$. We determine an r-band absolute magnitude of $M_{r} = 11.4$, consistent with a mid-M dwarf, and an approximate distance to the source of $2.2$ kpc. Using classical-flare models, we infer a flare energy of $E_{V} \simeq (4.1\pm 2.2)\times 10^{36}$ ergs, making this one of the strongest flares documented on an M dwarf.