Simultaneous Multiwavelength Flare Observations of EV Lacertae

Abstract

We present the first results of our ongoing project conducting simultaneous multiwavelength observations of flares on nearby active M dwarfs. We acquired data of the nearby dM3.5e star EV Lac using five different observatories: NASA's Transiting Exoplanet Survey Satellite (TESS), NASA's Neil Gehrels Swift Observatory (Swift), NASA's Neutron Interior Composition Explorer (NICER), the University of Hawaii 2.2-meter telescope (UH88), and the Las Cumbres Observatory Global Telescope (LCOGT) Network. During the ∼25 days of TESS observations, we acquired three simultaneous UV/X-ray observations using Swift that total ∼18 ks, 21 simultaneous epochs totaling ∼98 ks of X-ray data using NICER, one observation (∼3 hr) with UH88, and one observation (∼3 hr) with LCOGT. We identified 56 flares in the TESS light curve with estimated energies in the range log ET (erg) = (30.5–33.2), nine flares in the Swift UVM2 light curve with estimated energies in the range log EUV (erg) = (29.3–31.1), 14 flares in the NICER light curve with estimated minimum energies in the range log EN (erg) = (30.5–32.3), and 1 flare in the LCOGT light curve with log EL (erg) = 31.6. We find that the flare frequency distributions (FFDs) of TESS and NICER flares have comparable slopes, βᴛ = −0.67 ± 0.09 and βᶰ = − 0.65 ± 0.19, and the FFD of UVOT flares has a shallower slope (βᴜ = −0.38 ± 0.13). Furthermore, we do not find conclusive evidence for either the first ionization potential (FIP) or the inverse FIP effect during coronal flares on EV Lac.