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dc.contributor.authorGully-Santiago, Michael A.
dc.contributor.authorHerczeg, Gregory J.
dc.contributor.authorCzekala, Ian
dc.contributor.authorSomers, Garrett
dc.contributor.authorGrankin, Konstantin
dc.contributor.authorCovey, Kevin R.
dc.contributor.authorDonati, J. F.
dc.contributor.authorAlencar, Silvia H. P.
dc.contributor.authorHussain, Gaitee A. J.
dc.contributor.authorShappee, Benjamin J.
dc.contributor.authorMace, Gregory N.
dc.contributor.authorLee, Jae-Joon
dc.contributor.authorHoloien, T. W.-S.
dc.contributor.authorJose, Jessy
dc.contributor.authorLiu, Chun-Fan
dc.identifier.citationGully-Santiago , M A , Herczeg , G J , Czekala , I , Somers , G , Grankin , K , Covey , K R , Donati , J F , Alencar , S H P , Hussain , G A J , Shappee , B J , Mace , G N , Lee , J-J , Holoien , T W-S , Jose , J & Liu , C-F 2017 , ' Placing the spotted T Tauri star LkCa 4 on an HR diagram ' , Astrophysical Journal , vol. 836 , no. 2 , 200 .
dc.identifier.otherBibCode: 2017ApJ...836..200G
dc.identifier.otherORCID: /0000-0002-1483-8811/work/146464258
dc.description.abstractAges and masses of young stars are often estimated by comparing their luminosities and effective temperatures to pre-main-sequence stellar evolution tracks, but magnetic fields and starspots complicate both the observations and evolution. To understand their influence, we study the heavily spotted weak-lined T-Tauri star LkCa 4 by searching for spectral signatures of radiation originating from the starspot or starspot groups. We introduce a new methodology for constraining both the starspot filling factor and the spot temperature by fitting two-temperature stellar atmosphere models constructed from Phoenix synthetic spectra to a high-resolution near-IR IGRINS spectrum. Clearly discernable spectral features arise from both a hot photospheric component Thot ∼ 4100 K and a cool component Tcool ∼ 2700–3000 K, which covers ∼80% of the visible surface. This mix of hot and cool emission is supported by analyses of the spectral energy distribution, rotational modulation of colors and of TiO band strengths, and features in low-resolution optical/near-IR spectroscopy. Although the revised effective temperature and luminosity make LkCa 4 appear to be much younger and of much lower mass than previous estimates from unspotted stellar evolution models, appropriate estimates will require the production and adoption of spotted evolutionary models. Biases from starspots likely afflict most fully convective young stars and contribute to uncertainties in ages and age spreads of open clusters. In some spectral regions, starspots act as a featureless "veiling" continuum owing to high rotational broadening and heavy line blanketing in cool star spectra. Some evidence is also found for an anticorrelation between the velocities of the warm and cool components.
dc.relation.ispartofAstrophysical Journalen
dc.subjectStars: fundamental parametersen
dc.subjectStars: individual: LkCa 4en
dc.subjectStars: low-massen
dc.subjectStars: statisticsen
dc.subjectQB Astronomyen
dc.titlePlacing the spotted T Tauri star LkCa 4 on an HR diagramen
dc.typeJournal articleen
dc.contributor.institutionUniversity of St Andrews. School of Physics and Astronomyen
dc.contributor.institutionUniversity of St Andrews. University of St Andrewsen
dc.description.statusPeer revieweden

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