The Multiple Continuum Components in the White-Light Flare of 16 January 2009 on the dM4.5e Star YZ CMi

摘要

The white light during M dwarf flares has long been known to exhibit thebroadband shape of a T~10,000 K blackbody, and the white light in solar flaresis thought to arise primarily from Hydrogen recombination. Yet, a current lackof broad wavelength coverage solar-flare spectra in the optical/near-UVprohibits a direct comparison of the continuum properties to determine if theyare indeed so different. New spectroscopic observations of a secondary flareduring the decay of a megaflare on the dM4.5e star YZ CMi have revealedmultiple components in the white-light continuum of stellar flares, includingboth a blackbody-like spectrum and a hydrogen recombination spectrum. One ofthe most surprising findings is that these two components are anti-correlatedin their temporal evolution. We combine initial phenomenological modeling ofthe continuum components with spectra from radiative-hydrodynamic models toshow that continuum veiling gives rise to the measured anti-correlation. Thismodeling allows us to use the components' inferred properties to predict how asimilar spatially resolved, multiple-component white-light continuum mightappear using analogies to several solar flare phenomena. We also compare theproperties of the optical stellar flare white light to Ellerman bombs on theSun.