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dc.contributor.authorFrance, Kevin
dc.contributor.authorDuvvuri, Girish
dc.contributor.authorEgan, Hilary
dc.contributor.authorKoskinen, Tommi
dc.contributor.authorWilson, David J.
dc.contributor.authorYoungblood, Allison
dc.contributor.authorFroning, Cynthia S.
dc.contributor.authorBrown, Alexander
dc.contributor.authorAlvarado-Gómez, Julián D.
dc.contributor.authorBerta-Thompson, Zachory K.
dc.contributor.authorDrake, Jeremy J.
dc.contributor.authorGarraffo, Cecilia
dc.contributor.authorKaltenegger, Lisa
dc.contributor.authorKowalski, Adam F.
dc.contributor.authorLinsky, Jeffrey L.
dc.contributor.authorLoyd, R. O. Parke
dc.contributor.authorMauas, Pablo J. D.
dc.contributor.authorMiguel, Yamila
dc.contributor.authorPineda, J. Sebastian
dc.contributor.authorRugheimer, Sarah
dc.contributor.authorSchneider, P. Christian
dc.contributor.authorTian, Feng
dc.contributor.authorVieytes, Mariela
dc.date.accessioned2021-02-09T23:19:22Z
dc.date.available2021-02-09T23:19:22Z
dc.date.issued2020-10-30
dc.identifier.citationFrance, K., Duvvuri, G., Egan, H., Koskinen, T., Wilson, D. J., Youngblood, A., ... & Vieytes, M. (2020). The High-energy Radiation Environment around a 10 Gyr M Dwarf: Habitable at Last?. The Astronomical Journal, 160(5), 237.en_US
dc.identifier.issn0004-6256
dc.identifier.doi10.3847/1538-3881/abb465
dc.identifier.urihttp://hdl.handle.net/10150/652227
dc.description.abstractRecent work has demonstrated that high levels of X-ray and UV activity on young M dwarfs may drive rapid atmospheric escape on temperate, terrestrial planets orbiting within the habitable zone. However, secondary atmospheres on planets orbiting older, less active M dwarfs may be stable and present more promising candidates for biomarker searches. In order to evaluate the potential habitability of Earth-like planets around old, inactive M dwarfs, we present new Hubble Space Telescope and Chandra X-ray Observatory observations of Barnard's Star (GJ 699), a 10 Gyr old M3.5 dwarf, acquired as part of the Mega-MUSCLES program. Despite the old age and long rotation period of Barnard's Star, we observe two FUV (delta(130) 5000 s; E-130 10(29.5) erg each) and one X-ray (E-X 10(29.2) erg) flares, and we estimate a high-energy flare duty cycle (defined here as the fraction of the time the star is in a flare state) of similar to 25%. A publicly available 5 A to 10 mu m spectral energy distribution of GJ 699 is created and used to evaluate the atmospheric stability of a hypothetical, unmagnetized terrestrial planet in the habitable zone (r(HZ) similar to 0.1 au). Both thermal and nonthermal escape modeling indicate (1) the quiescent stellar XUV flux does not lead to strong atmospheric escape: atmospheric heating rates are comparable to periods of high solar activity on modern Earth, and (2) the flare environment could drive the atmosphere into a hydrodynamic loss regime at the observed flare duty cycle: sustained exposure to the flare environment of GJ 699 results in the loss of 87 Earth atmospheres Gyr(-1) through thermal processes and 3 Earth atmospheres Gyr(-1) through ion loss processes. These results suggest that if rocky planet atmospheres can survive the initial similar to 5 Gyr of high stellar activity, or if a second-generation atmosphere can be formed or acquired, the flare duty cycle may be the controlling stellar parameter for the stability of Earth-like atmospheres around old M stars.en_US
dc.description.sponsorshipSpace Telescope Science Instituteen_US
dc.language.isoenen_US
dc.publisherIOP PUBLISHING LTDen_US
dc.rights© 2020. The American Astronomical Society. All rights reserved.en_US
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en_US
dc.subjectSolar extreme ultraviolet emissionen_US
dc.subjectExoplanet atmospheresen_US
dc.subjectStellar activityen_US
dc.subjectStellar flaresen_US
dc.subjectHabitable zoneen_US
dc.subjectHubble Space Telescopeen_US
dc.titleThe High-energy Radiation Environment around a 10 Gyr M Dwarf: Habitable at Last?en_US
dc.typeArticleen_US
dc.identifier.eissn1538-3881
dc.contributor.departmentUniv Arizona, Lunar & Planetary Laben_US
dc.identifier.journalASTRONOMICAL JOURNALen_US
dc.description.collectioninformationThis 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.en_US
dc.eprint.versionFinal published versionen_US
dc.source.journaltitleThe Astronomical Journal
dc.source.volume160
dc.source.issue5
dc.source.beginpage237
refterms.dateFOA2021-02-09T23:19:32Z


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