J/ApJ/763/L26ivo://CDS.VizieR/J/ApJ/763/L26doi:10.26093/cds/vizier.17639026CDSMetcalfe T.S.Buccino A.P.Brown B.P.Mathur S.Soderblom D.R.,Henry T.J.Mauas P.J.D.Petrucci R.Hall J.C.Basu S.2017-06-26T11:49:34Z2014-11-05T09:50:24ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frk-starsmultiple-starsThe active K2 dwarf {epsilon} Eri has been extensively characterized both as a young solar analog and more recently as an exoplanet host star. As one of the nearest and brightest stars in the sky, it provides an unparalleled opportunity to constrain stellar dynamo theory beyond the Sun. We confirm and document the 3-year magnetic activity cycle in {epsilon} Eri originally reported by Hatzes and coworkers (2000ApJ...544L.145H), and we examine the archival data from previous observations spanning 45 years. The data show coexisting 3-year and 13-year periods leading into a broad activity minimum that resembles a Maunder minimum-like state, followed by the resurgence of a coherent 3-year cycle. The nearly continuous activity record suggests the simultaneous operation of two stellar dynamos with cycle periods of 2.95+/-0.03yr and 12.7+/-0.3 years, which, by analogy with the solar case, suggests a revised identification of the dynamo mechanisms that are responsible for the so-called "active" and "inactive" sequences as proposed by B\"ohm-Vitense (2007ApJ...657..486B). Finally, based on the observed properties of {epsilon} Eri, we argue that the rotational history of the Sun is what makes it an outlier in the context of magnetic cycles observed in other stars (as also suggested by its Li depletion), and that a Jovian-mass companion cannot be the universal explanation for the solar peculiarities.2013ApJ...763L..26Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/763/L26CatalogResearchIsServedByTAP VizieR generic servicerelated-toIII/185 : Search for Jupiter-Mass Companions (Walker+, 1995)III/159 : Ca II H and K Measurements Made at MWO (Duncan+ 1991)J/A+A/552/A27 : Stellar activity and kinematics of FGK stars (Murgas+, 2013)J/A+A/551/L8 : Chromospheric activity of field stars (Pace, 2013)J/A+A/537/A147 : Optimizing exoplanet transit searches (Herrero+, 2012)J/ApJS/200/15 : HARPS-TERRA project. I. (Anglada-Escude+, 2012)J/ApJ/756/46 : Lithium abundances in HIP stars (Ramirez+, 2012)J/ApJ/744/138 : Calibrated visibilities of {epsilon} Eri (Baines+, 2012)J/AZh/88/1217 : Solar-like activity of low-mass stars (Kasova+, 2011)J/ApJ/725/875 : Chromospheric activity for CPS stars (Isaacson+, 2010)J/ApJ/724/154 : Lithium abundances in stars with planets (Ghezzi+, 2010)J/MNRAS/403/1368 : Li abundances for star-planet systems (Gonzalez+, 2010)J/A+A/483/903 : Mount Wilson index for F-K stars (Buccino+, 2008)J/A+A/469/309 : Late-type stars chromospheric activity (Cincunegui+, 2007)J/ApJ/640/1051 : 25pc sample of Sun-like stars (Grether+, 2006)J/MNRAS/372/163 : Activity indices for southern stars (Jenkins+, 2006)J/MNRAS/361/1102 : Spectrum of {epsilon} Eri (Sim+, 2005)J/PASJ/57/45 : Lithium abundances of F-K stars (Takeda+, 2005)J/ApJS/152/261 : Chromospheric Ca II emission in nearby stars (Wright+, 2004)J/A+A/416/281 : X-ray spectra of 4 cool stars (Sanz-Forcada+, 2004)J/A+A/409/251 : Li abundances & velocities in F and G stars (Mallik+, 2003)J/AJ/111/439 : Chromospheric emission in late-type stars. (Henry+ 1996)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/763/L26https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/763/L26http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/763/L26https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/763/L26https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/763/L26http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/763/L26GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJ/763/L26/table1Journal of SMARTS Observations for {epsilon} ErirecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsDate of the observation (UT)stime.epochnullableBJDBarycentric Julian Date of observation; BJD+2450000dtime.epochdoubleS(MWO)[0.39/0.64] Measured Mount Wilson S-indexphot.flux;arith.ratiofloate_S(MWO)Uncertainty in S(MWO)stat.errorfloat