Semi-empirical Modeling of the Photosphere, Chromosphere, Transition Region, and Corona of the M-dwarf Host Star GJ 832
| Autor: | J. M. Fontenla, Jeffrey L. Linsky, Jesse Garrison, Kevin France, A. Buccino, Pablo Mauas, Mariela Vieytes, Lucianne M. Walkowicz |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
coronae [stars]
010504 meteorology & atmospheric sciences Ciencias Físicas stars [ultraviolet] FOS: Physical sciences Astrophysics Star (graph theory) 01 natural sciences Coronal radiative losses purl.org/becyt/ford/1 [https] 0103 physical sciences Astrophysics::Solar and Stellar Astrophysics 010303 astronomy & astrophysics Chromosphere planetstar interactions individual: GJ 832 [stars] Astrophysics::Galaxy Astrophysics Solar and Stellar Astrophysics (astro-ph.SR) 0105 earth and related environmental sciences Physics Photosphere Astronomy Astronomy and Astrophysics purl.org/becyt/ford/1.3 [https] Corona Astronomía chromospheres [stars] Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Physics::Space Physics late-type [stars] Astrophysics::Earth and Planetary Astrophysics CIENCIAS NATURALES Y EXACTAS |
| Zdroj: | CONICET Digital (CONICET) Consejo Nacional de Investigaciones Científicas y Técnicas instacron:CONICET |
| DOI: | 10.48550/arxiv.1608.00934 |
| Popis: | Stellar radiation from X-rays to the visible provides the energy that controls the photochemistry and mass loss from exoplanet atmospheres. The important extreme ultraviolet (EUV) region (10--91.2~nm) is inaccessible and should be computed from a reliable stellar model. It is essential to understand the formation regions and physical processes responsible for the various stellar emission features in order to predict how the spectral energy distribution varies with age and activity levels. We compute a state-of-the-art semi-empirical atmospheric model and the emergent high-resolution synthetic spectrum of the moderately active M2~V star GJ~832 as the first of a series of models for stars with different activity levels. Using non-LTE radiative transfer techniques and including many molecular lines, we construct a one-dimensional simple model for the physical structure of the star's chromosphere, chromosphere-corona transition region, and corona. The synthesized spectrum for this model fits the continuum and lines across the UV to optical spectrum. Particular emphasis is given to the emission lines at wavelengths shorter than 300~nm observed with {\em HST}, which have important effects on the photochemistry in the exoplanet atmospheres. The FUV line ratios indicate that the transition region of GJ~832 is more biased to hotter material than that of the quiet Sun. The excellent agreement of our computed EUV luminosity with that obtained by two other techniques indicates that our model predicts reliable EUV emission from GJ~832. We find that unobserved EUV flux of GJ~832, which heats the outer atmospheres of exoplanets and drives their mass loss, is comparable to the active Sun. Comment: Accepted for publication by the Astrophysical Journal, 63 pages, 12 figures |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|