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Title: The intrinsic extreme ultraviolet fluxes of F5 V to M5 V stars

Extreme ultraviolet (EUV) radiations (10-117 nm) from host stars play important roles in the ionization, heating, and mass loss from exoplanet atmospheres. Together with the host star's Lyα and far-UV (117-170 nm) radiation, EUV radiation photodissociates important molecules, thereby changing the chemistry in exoplanet atmospheres. Since stellar EUV fluxes cannot now be measured and interstellar neutral hydrogen completely obscures stellar radiation between 40 and 91.2 nm, even for the nearest stars, we must estimate the unobservable EUV flux by indirect methods. New non-LTE semiempirical models of the solar chromosphere and corona and solar irradiance measurements show that the ratio of EUV flux in a variety of wavelength bands to the Lyα flux varies slowly with the Lyα flux and thus with the magnetic heating rate. This suggests and we confirm that solar EUV/Lyα flux ratios based on the models and observations are similar to the available 10-40 nm flux ratios observed with the Extreme Ultraviolet Explorer (EUVE) satellite and the 91.2-117 nm flux observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite for F5 V-M5 V stars. We provide formulae for predicting EUV flux ratios based on the EUVE and FUSE stellar data and on the solar models, which aremore » essential input for modeling the atmospheres of exoplanets.« less
Authors:
 [1] ;  [2] ;  [3]
  1. JILA, University of Colorado and NIST, 440UCB Boulder, CO 80309-0440 (United States)
  2. NorthWest Research Associates Inc., 3380 Mitchell Ln, Boulder, CO 80301 (United States)
  3. CASA, University of Colorado, 593UCB Boulder, CO 80309-0593 (United States)
Publication Date:
OSTI Identifier:
22348315
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 780; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHROMOSPHERE; EXTREME ULTRAVIOLET RADIATION; FAR ULTRAVIOLET RADIATION; HEATING RATE; HYDROGEN; INTERACTIONS; LTE; MASS TRANSFER; PLANETS; RADIANT FLUX DENSITY; SATELLITE ATMOSPHERES; SIMULATION; STAR MODELS; STARS; STELLAR RADIATION; STELLAR WINDS; SUN