M dwarf flares from time-resolved SDSS spectra

Abstract

Flares on low-mass dwarfs are a major source of variability in the optical and UV in the Galaxy. In addition to being a source of optical transients, these flares may have an important effect on the habitability of planets orbiting low-mass dwarfs. We present a study of flares on M dwarfs determined from Sloan Digital Sky Survey time-resolved spectra. Our sample consists of tens of thousands of M dwarfs whose SDSS spectra were formed from co-adds of several (typically 3-5) consecutive shorter (typically 9-15 minute) exposures. We present the Flare Line Index as a way to identify flares in these individual component spectra with crude time-resolution, and investigate the short-term variability of the Balmer and Ca II emission lines. © 2009 American Institute of Physics.