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Optical, UV, and X-ray evidence for a 7-yr stellar cycle in Proxima Centauri

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dc.abstract.enStars of stellar type later than about M3.5 are believed to be fully convective and therefore unable to support magnetic dynamos like the one that produces the 11-yr solar cycle. Because of their intrinsic faintness, very few late M stars have undergone long-term monitoring to test this prediction, which is critical to our understanding of magnetic field generation in such stars. Magnetic activity is also of interest as the driver of UV and X-ray radiation, as well as energetic particles and stellar winds, that affects the atmospheres of close-in planets that lie within habitable zones, such as the recently discovered Proxima b. We report here on several years of optical, UV, and X-ray observations of Proxima Centauri (GJ 551; dM5.5e): 15 yr of All Sky Automated Survey photometry in the V band (1085 nights) and 3 yr in the I band (196 nights), 4 yr of Swift X-Ray Telescope and UV/Optical Telescope observations (more than 120 exposures), and nine sets of X-ray observations from other X-ray missions (ASCA, XMM-Newton, and three Chandra instruments) spanning 22 yr. We confirm previous reports of an 83-d rotational period and find strong evidence for a 7-yr stellar cycle, along with indications of differential rotation at about the solar level. X-ray/UV intensity is anticorrelated with optical V-band brightness for both rotational and cyclical variations. From comparison with other stars observed to have X-ray cycles, we deduce a simple empirical relationship between X-ray cyclic modulation and Rossby number, and we also present Swift UV grism spectra covering 2300-6000 Å.
dc.affiliationUniwersytet Warszawski
dc.contributor.authorWargelin, B. J.
dc.contributor.authorSaar, S. H.
dc.contributor.authorPojmański, Grzegorz
dc.contributor.authorDrake, J. J.
dc.contributor.authorKashyap, V. L.
dc.date.accessioned2024-01-25T15:58:25Z
dc.date.available2024-01-25T15:58:25Z
dc.date.copyright2016-10-11
dc.date.issued2017
dc.description.accesstimeBEFORE_PUBLICATION
dc.description.financeNie dotyczy
dc.description.number3
dc.description.versionORIGINAL_AUTHOR
dc.description.volume464
dc.identifier.doi10.1093/MNRAS/STW2570
dc.identifier.issn0035-8711
dc.identifier.urihttps://repozytorium.uw.edu.pl//handle/item/114983
dc.identifier.weblinkhttp://adsabs.harvard.edu/abs/2017MNRAS.464.3281W
dc.languageeng
dc.pbn.affiliationastronomy
dc.relation.ispartofMonthly Notices of the Royal Astronomical Society
dc.relation.pages3281-3296
dc.rightsOther
dc.sciencecloudnosend
dc.titleOptical, UV, and X-ray evidence for a 7-yr stellar cycle in Proxima Centauri
dc.typeJournalArticle
dspace.entity.typePublication