A study of flares on EV Lacertae using simultaneous multi-wavelength data

Abstract

We present the first results from our large program studying nearby active flaring M dwarfs using multi-wavelength datasets. We focus on the flaring M dwarf EV Lac, which has been known as a flare star for at least 65 years. We acquired data of EV Lac using 5 different observatories: NASA’s TESS mission, NASA’s Neil Gehrels Swift Observatory (Swift), NASA’s Neutron Interior Composition Explorer (NICER) and two ground based telescopes (University of Hawaii 2.2-m (UH88) and Las Cumbres Observatory Global Telescope (LCOGT) Network), to span a comprehensive, simultaneous wavelength coverage of flaring events. We identified 56 flares in the TESS light curve, 9 flares in the Swift UVM2 light curve, 14 flares in the NICER X-ray light curve, and 1 flare in the LCOGT light curve. However, we did not identify flares in the Swift XRT light curve or UH88 spectrum. We find that the FFDs of TESS and NICER flares have comparable slopes, βᴛ = -0.67±0.09 and βᶰ = -0.65±0.19, and that the FFD of UVOT flares has a shallower slope (βᴜ = -0.38±0.13). Our results will be useful to model and estimate the impacts of strong flares on the atmospheres of planets orbiting M dwarfs.