<i>KEPLER</i>FLARES. I. ACTIVE AND INACTIVE M DWARFS

Abstract

We analyzed Kepler short-cadence M dwarf observations. Spectra from the ARC\n3.5m telescope identify magnetically active (H$\\alpha$ in emission) stars. The\nactive stars are of mid-M spectral type, have numerous flares, and well-defined\nrotational modulation due to starspots. The inactive stars are of early-M type,\nexhibit less starspot signature, and have fewer flares. A Kepler to U-band\nenergy scaling allows comparison of the Kepler flare frequency distributions\nwith previous ground-based data. M dwarfs span a large range of flare frequency\nand energy, blurring the distinction between active and inactive stars\ndesignated solely by the presence of H$\\alpha$. We analyzed classical and\ncomplex (multiple peak) flares on GJ 1243, finding strong correlations between\nflare energy, amplitude, duration and decay time, with only a weak dependence\non rise time. Complex flares last longer and have higher energy at the same\namplitude, and higher energy flares are more likely to be complex. A power law\nfits the energy distribution for flares with log $E_{K_p} &gt;$ 31 ergs, but the\npredicted number of low energy flares far exceeds the number observed, at\nenergies where flares are still easily detectable, indicating that the power\nlaw distribution may flatten at low energy. There is no correlation of flare\noccurrence or energy with starspot phase; the flare waiting time distribution\nis consistent with flares occurring randomly in time; and the energies of\nconsecutive flares are uncorrelated. These observations support a scenario\nwhere many independent active regions on the stellar surface are contributing\nto the observed flare rate.\n