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Article Dans Une Revue The Astrophysical Journal Année : 2017

Placing the Spotted T Tauri Star LkCa 4 on an HR Diagram

Michael A. Gully-Santiago
  • Fonction : Auteur
Gregory J. Herczeg
  • Fonction : Auteur
Ian Czekala
  • Fonction : Auteur
Garrett Somers
  • Fonction : Auteur
Konstantin Grankin
  • Fonction : Auteur
Kevin R. Covey
  • Fonction : Auteur
Silvia H. P. Alencar
  • Fonction : Auteur
Gaitee A. J. Hussain
  • Fonction : Auteur
Benjamin J. Shappee
  • Fonction : Auteur
Gregory N. Mace
  • Fonction : Auteur
Jae-Joon Lee
  • Fonction : Auteur
T. W. -S. Holoien
  • Fonction : Auteur
Jessy Jose
  • Fonction : Auteur
Chun-Fan Liu
  • Fonction : Auteur

Résumé

Ages 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 {T}{hot} ∼ 4100 K and a cool component {T}{cool} ∼ 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.

Dates et versions

insu-03677083 , version 1 (24-05-2022)

Identifiants

Citer

Michael A. Gully-Santiago, Gregory J. Herczeg, Ian Czekala, Garrett Somers, Konstantin Grankin, et al.. Placing the Spotted T Tauri Star LkCa 4 on an HR Diagram. The Astrophysical Journal, 2017, 836, ⟨10.3847/1538-4357/836/2/200⟩. ⟨insu-03677083⟩
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