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    HAZMAT VI: The Evolution of Extreme Ultraviolet Radiation Emitted from Early M Stars

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    Peacock_2020_ApJ_895_5.pdf
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    Author
    Peacock, Sarah cc
    Barman, Travis
    Shkolnik, Evgenya L.
    Loyd, R. O. Parke cc
    Schneider, Adam C.
    Pagano, Isabella
    Meadows, Victoria S.
    Affiliation
    Univ Arizona, Lunar & Planetary Lab
    Issue Date
    2020-05-19
    Keywords
    Stellar activity
    Stellar chromospheres
    Low mass stars
    M stars
    Ultraviolet astronomy
    Stellar evolution
    
    Metadata
    Show full item record
    Publisher
    IOP PUBLISHING LTD
    Citation
    Peacock, S., Barman, T., Shkolnik, E. L., Loyd, R. P., Schneider, A. C., Pagano, I., & Meadows, V. S. (2020). HAZMAT VI: The Evolution of Extreme Ultraviolet Radiation Emitted from Early M Stars. The Astrophysical Journal, 895(1), 5.
    Journal
    ASTROPHYSICAL JOURNAL
    Rights
    © 2020. The American Astronomical Society. All rights reserved.
    Collection Information
    This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.
    Abstract
    Quantifying the evolution of stellar extreme ultraviolet (EUV, 100-1000 A) emission is critical for assessing the evolution of planetary atmospheres and the habitability of M dwarf systems. Previous studies from the HAbitable Zones and M dwarf Activity across Time (HAZMAT) program showed the far- and near-UV (FUV, NUV) emission from M stars at various stages of a stellar lifetime through photometric measurements from the Galaxy Evolution Explorer (GALEX). The results revealed increased levels of short-wavelength emission that remain elevated for hundreds of millions of years. The trend for EUV flux as a function of age could not be determined empirically because absorption by the interstellar medium prevents access to the EUV wavelengths for the vast majority of stars. In this paper, we model the evolution of EUV flux from early M stars to address this observational gap. We present synthetic spectra spanning EUV to infrared wavelengths of 0.4 0.05 M-& x2609; stars at five distinct ages between 10 and 5000 Myr, computed with the PHOENIX atmosphere code and guided by the GALEX photometry. We model a range of EUV fluxes spanning two orders of magnitude, consistent with the observed spread in X-ray, FUV, and NUV flux at each epoch. Our results show that the stellar EUV emission from young M stars is 100 times stronger than field age M stars, and decreases as t(-1) after remaining constant for a few hundred million years. This decline stems from changes in the chromospheric temperature structure, which steadily shifts outward with time. Our models reconstruct the full spectrally and temporally resolved history of an M star's UV radiation, including the unobservable EUV radiation, which drives planetary atmospheric escape, directly impacting a planet's potential for habitability.
    ISSN
    0004-637X
    EISSN
    1538-4357
    DOI
    10.3847/1538-4357/ab893a
    Version
    Final published version
    Sponsors
    NASA Earth and Space Science Fellowship Program
    ae974a485f413a2113503eed53cd6c53
    10.3847/1538-4357/ab893a
    Scopus Count
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    UA Faculty Publications

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