A White-light Flare on the L1 Dwarf WISEP J190648.47+401106.8

Abstract

WISEP J190648.47+401106.8 is an L1 brown dwarf known for a powerful 2012 flare observed by Gemini North. Although M dwarf flares are common and well-studied, flares on cooler L dwarfs are less understood. We perform a time series analysis of spectroscopic data obtained during the event of the flare to investigate the temporal evolution of the Hα emission feature. We find an inverse relationship between peak amplitude and equivalent width, indicating that the emission feature narrows as the flare intensifies. Additionally, we modeled the white flare spectrum by adding a blackbody element component to a quiescent spectrum. The fits suggest a blackbody temperature of 12,850 ± 25 K during the flare, which is consistent with flare temperatures observed in early-type M dwarfs. These results offer insight into the heating process of magnetic activity in ultracool dwarfs, and highlight the need for UV observations to break the temperature-filling factor degeneracy.