Measuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH Lines
As part of the Young Exoplanets Spectroscopic Survey, this study explores the spot variability of 13 T Tauri Stars (TTSs) in the near-infrared H band, using spectra from the Immersion GRating INfrared Spectrometer. By analyzing effective temperature ( T _eff ) sensitive lines of atomic Fe i at ∼1.56...
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2024-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ad5e7f |
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| author | Shih-Yun Tang Christopher M. Johns-Krull L. Prato Asa G. Stahl |
| author_facet | Shih-Yun Tang Christopher M. Johns-Krull L. Prato Asa G. Stahl |
| author_sort | Shih-Yun Tang |
| collection | DOAJ |
| description | As part of the Young Exoplanets Spectroscopic Survey, this study explores the spot variability of 13 T Tauri Stars (TTSs) in the near-infrared H band, using spectra from the Immersion GRating INfrared Spectrometer. By analyzing effective temperature ( T _eff ) sensitive lines of atomic Fe i at ∼1.56259 μ m and ∼1.56362 μ m, and molecular OH at ∼1.56310 and ∼1.56317 μ m, we develop an empirical equivalent width ratio (EWR) relationship for T _eff in the range of 3400–5000 K. This relationship allows for precise relative T _eff estimates to within tens of Kelvin and demonstrates compatibility with solar metallicity target models. However, discrepancies between observational data and model predictions limit the extension of the T _eff –EWR relationship to a broader parameter space. Our study reveals that both classical and weak-line TTSs can exhibit T _eff variations exceeding 150 K over a span of 2 yr. The detection of a quarter-phase delay between the EWR and radial velocity phase curves in TTSs indicates spot-driven signals. A phase delay of 0.06 ± 0.13 for CI Tau, however, suggests additional dynamics, potentially caused by planetary interaction, inferred from a posited 1:1 commensurability between the rotation period and orbital period. Moreover, a positive correlation between T _eff variation amplitude and stellar inclination angle supports the existence of high-latitude spots on TTSs, further enriching our understanding of stellar surface activity in young stars. |
| format | Article |
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| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
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| spelling | doaj-art-e79010b885af4bb1a99080b5e4ea2f2c2025-08-20T02:39:59ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-01973212410.3847/1538-4357/ad5e7fMeasuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH LinesShih-Yun Tang0https://orcid.org/0000-0003-4247-1401Christopher M. Johns-Krull1https://orcid.org/0000-0002-8828-6386L. Prato2https://orcid.org/0000-0001-7998-226XAsa G. Stahl3https://orcid.org/0000-0002-0848-6960Department of Physics and Astronomy, Rice University , 6100 Main Street, Houston, TX 77005, USA ; sytang@rice.edu; Lowell Observatory , 1400 West Mars Hill Road, Flagstaff, AZ 86001, USADepartment of Physics and Astronomy, Rice University , 6100 Main Street, Houston, TX 77005, USA ; sytang@rice.eduLowell Observatory , 1400 West Mars Hill Road, Flagstaff, AZ 86001, USADepartment of Physics and Astronomy, Rice University , 6100 Main Street, Houston, TX 77005, USA ; sytang@rice.eduAs part of the Young Exoplanets Spectroscopic Survey, this study explores the spot variability of 13 T Tauri Stars (TTSs) in the near-infrared H band, using spectra from the Immersion GRating INfrared Spectrometer. By analyzing effective temperature ( T _eff ) sensitive lines of atomic Fe i at ∼1.56259 μ m and ∼1.56362 μ m, and molecular OH at ∼1.56310 and ∼1.56317 μ m, we develop an empirical equivalent width ratio (EWR) relationship for T _eff in the range of 3400–5000 K. This relationship allows for precise relative T _eff estimates to within tens of Kelvin and demonstrates compatibility with solar metallicity target models. However, discrepancies between observational data and model predictions limit the extension of the T _eff –EWR relationship to a broader parameter space. Our study reveals that both classical and weak-line TTSs can exhibit T _eff variations exceeding 150 K over a span of 2 yr. The detection of a quarter-phase delay between the EWR and radial velocity phase curves in TTSs indicates spot-driven signals. A phase delay of 0.06 ± 0.13 for CI Tau, however, suggests additional dynamics, potentially caused by planetary interaction, inferred from a posited 1:1 commensurability between the rotation period and orbital period. Moreover, a positive correlation between T _eff variation amplitude and stellar inclination angle supports the existence of high-latitude spots on TTSs, further enriching our understanding of stellar surface activity in young stars.https://doi.org/10.3847/1538-4357/ad5e7fPre-main sequence starsStellar effective temperaturesInfrared spectroscopyStellar spectral linesStarspots |
| spellingShingle | Shih-Yun Tang Christopher M. Johns-Krull L. Prato Asa G. Stahl Measuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH Lines The Astrophysical Journal Pre-main sequence stars Stellar effective temperatures Infrared spectroscopy Stellar spectral lines Starspots |
| title | Measuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH Lines |
| title_full | Measuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH Lines |
| title_fullStr | Measuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH Lines |
| title_full_unstemmed | Measuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH Lines |
| title_short | Measuring the Spot Variability of T Tauri Stars Using Near-infrared Atomic Fe and Molecular OH Lines |
| title_sort | measuring the spot variability of t tauri stars using near infrared atomic fe and molecular oh lines |
| topic | Pre-main sequence stars Stellar effective temperatures Infrared spectroscopy Stellar spectral lines Starspots |
| url | https://doi.org/10.3847/1538-4357/ad5e7f |
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