Near-Ultraviolet Spectra of Flares on YZ CMi

Abstract

Near-ultraviolet spectroscopic data obtained with the HST STIS instrument on the dMe flare star YZ Canis Minoris (YZ CMi) were analyzed. Flare and quiet intervals were identified from the broadband near-UV light curve, and the spectrum of each flare was separately extracted. Mg II and Fe II line profiles show similar behavior during the flares. Two large flares allowed time-resolved spectra to be analyzed, revealing a very broad component to the Mg II k line profile in at least one flare spectrum (F9b). If interpreted as a velocity, this component requires chromospheric material to be moving with FWHM ~ 250 km/sec, implying kinetic energy far in excess of the radiative energy. The Mg II k flare line profiles were compared to recent radiative hydrodynamic models of flare atmospheres undergoing electron beam heating. The models successfully predict red enhancements in the line profile with typical velocity of a few km/sec, but do not reproduce the flares showing blue enhancements, or the strongly broadened line observed in flare F9b. A more complete calculation of redistribution into the line wings, including the effect of collisions with the electron beam, may resolve the origin of the excess line broadening.

29 pages, 12 figures; accepted to PASP

References in corpus (1)

• Radiative Hydrodynamic Models of Optical and Ultraviolet Emission from M Dwarf Flares

Cited by in corpus (17)

• Do Kepler superflare stars really include slowly-rotating Sun-like stars ? - Results using APO 3.5m telescope spectroscopic observations and Gaia-DR2 data -
• The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares I: Modeling the Brightest NUV Footpoints in the X1 Solar Flare of 2014 March 29
• The High-Energy Radiation Environment Around a 10 Gyr M Dwarf: Habitable at Last?
• EvryFlare III: Temperature Evolution and Habitability Impacts of Dozens of Superflares Observed Simultaneously by Evryscope and TESS
• Hydrogen Balmer Line Broadening in Solar and Stellar Flares
• Characterizing the Near-UV Environment of M Dwarfs
• Modeling Mg II h, k and Triplet Lines at Solar Flare Ribbons
• APO & SMARTS flare star campaign observations I. Blue wing asymmetries in chromospheric lines during mid M dwarf flares from simultaneous spectroscopic and photometric observation data
• The Far Ultraviolet M-dwarf Evolution Survey. I. The Rotational Evolution of High-Energy Emissions
• The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. II. Hydrogen Broadening Predictions for Solar Flare Observations with the Daniel K. Inouye Solar Telescope
• Extending Optical Flare Models to the UV: Results from Comparing of TESS and GALEX Flare Observations For M Dwarfs
• Constraints on Stellar Flare Energy Ratios in the NUV and Optical From a Multiwavelength Study of GALEX and Kepler Flare Stars
• A $\Delta R\sim 9.5$ mag Super Flare of An Ultracool Star Detected by $\text{SVOM/GWAC}$ System
• Characterisation of the NUV and Optical Emission and Temperature of Flares from Ross 733 with Swift and TESS
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)
• Young M dwarfs flare activity model: Towards better exoplanetary atmospheric characterisation
• The M-dwarf Ultraviolet Spectroscopic Sample I. Determining Stellar Parameters for Field Stars