A Pilot Survey of an M Dwarf Flare Star with Swift's UV Grism

TL;DR

This study used Swift's UV Grism to observe flares on the young M dwarf AU Mic, detecting multiple flares and elevated activity, providing insights into stellar flare behavior and energy release in the NUV spectrum.

Contribution

First NUV spectroscopic survey of AU Mic's flares, revealing flare rates, energies, and durations with implications for stellar and exoplanetary environments.

Findings

Detected four flares and elevated activity during 9.6 hours of observation.

Largest flare released at least 6×10^33 erg of energy.

Flares lasted longer than 14-17 minutes, complicating total energy measurement.

Abstract

The near-ultraviolet (NUV) spectral region is a useful diagnostic for stellar flare physics and assessing the energy environment of young exoplanets, especially as relates to prebiotic chemistry. We conducted a pilot NUV spectroscopic flare survey of the young M dwarf AU Mic with the Neil Gehrels Swift Observatory's UltraViolet and Optical Telescope. We detected four flares and three other epochs of significantly elevated count rates during the 9.6 hours of total exposure time, consistent with a NUV flare rate of $\sim$0.5 hour$^{-1}$. The largest flare we observed released a minimum energy of 6$\times$10$^{33}$ erg between 1730-5000 \r{A}. All flares had durations longer than the $\sim$14-17 minute duration of each Swift visit, making measuring total flare energy and duration infeasible.