Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4
We present a multi-epoch spectroscopic study of LkCa 4, a heavily spotted non-accreting T Tauri star. Using SpeX at NASA’s Infrared Telescope Facility (IRTF), 12 spectra were collected over five consecutive nights, spanning ≈1.5 stellar rotations. Using the IRTF SpeX Spectral Library, we constructed...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acbb61 |
| _version_ | 1827830868484292608 |
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| author | Facundo Pérez Paolino Jeffrey S. Bary Michael S. Petersen Kimberly Ward-Duong Benjamin M. Tofflemire Katherine B. Follette Heidi Mach |
| author_facet | Facundo Pérez Paolino Jeffrey S. Bary Michael S. Petersen Kimberly Ward-Duong Benjamin M. Tofflemire Katherine B. Follette Heidi Mach |
| author_sort | Facundo Pérez Paolino |
| collection | DOAJ |
| description | We present a multi-epoch spectroscopic study of LkCa 4, a heavily spotted non-accreting T Tauri star. Using SpeX at NASA’s Infrared Telescope Facility (IRTF), 12 spectra were collected over five consecutive nights, spanning ≈1.5 stellar rotations. Using the IRTF SpeX Spectral Library, we constructed empirical composite models of spotted stars by combining a warmer (photosphere) standard star spectrum with a cooler (spot) standard weighted by the spot filling factor, f _spot . The best-fit models spanned two photospheric component temperatures, T _phot = 4100 K (K7V) and 4400 K (K5V), and one spot component temperature, T _spot = 3060 K (M5V) with an A _V of 0.3. We find values of f _spot to vary between 0.77 and 0.94 with an average uncertainty of ∼0.04. The variability of f _spot is periodic and correlates with its 3.374 day rotational period. Using a mean value for f ^mean _spot to represent the total spot coverage, we calculated spot corrected values for T _eff and L _⋆ . Placing these values alongside evolutionary models developed for heavily spotted young stars, we infer mass and age ranges of 0.45–0.6 M _⊙ and 0.50–1.25 Myr, respectively. These inferred values represent a twofold increase in the mass and a twofold decrease in the age as compared to standard evolutionary models. Such a result highlights the need for constraining the contributions of cool and warm regions of young stellar atmospheres when estimating T _eff and L _⋆ to infer masses and ages as well as the necessity for models to account for the effects of these regions on the early evolution of low-mass stars. |
| first_indexed | 2024-03-12T04:36:16Z |
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| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T04:36:16Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-a6168b26348a42f39db3ad05aa8f90de2023-09-03T09:56:23ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194611010.3847/1538-4357/acbb61Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4Facundo Pérez Paolino0https://orcid.org/0000-0002-4128-7867Jeffrey S. Bary1https://orcid.org/0000-0001-8642-5867Michael S. Petersen2https://orcid.org/0000-0003-1517-3935Kimberly Ward-Duong3https://orcid.org/0000-0002-4479-8291Benjamin M. Tofflemire4https://orcid.org/0000-0003-2053-0749Katherine B. Follette5https://orcid.org/0000-0002-7821-0695Heidi Mach6Colgate University , 13 Oak Drive, Hamilton, NY 13346, USA ; jbary@colgate.eduColgate University , 13 Oak Drive, Hamilton, NY 13346, USA ; jbary@colgate.edu; Visiting astronomer at the NASA Infrared Telescope Facility , Mauna Kea Access Road, Hilo, HI 96720, USA 9Visiting astronomer at the NASA Infrared Telescope Facility , Mauna Kea Access Road, Hilo, HI 96720, USA 9; Institute for Astronomy, University of Edinburgh , Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UKVisiting astronomer at the NASA Infrared Telescope Facility , Mauna Kea Access Road, Hilo, HI 96720, USA 9; Department of Astronomy, Smith College , 10 Elm Street, Northampton, MA 01063, USADepartment of Astronomy, The University of Texas at Austin , Austin, TX 78712, USADepartment of Physics and Astronomy, Amherst College , Amherst, MA 01003, USAAllegheny College , 520 N. Main Street Meadville, PA 16335, USAWe present a multi-epoch spectroscopic study of LkCa 4, a heavily spotted non-accreting T Tauri star. Using SpeX at NASA’s Infrared Telescope Facility (IRTF), 12 spectra were collected over five consecutive nights, spanning ≈1.5 stellar rotations. Using the IRTF SpeX Spectral Library, we constructed empirical composite models of spotted stars by combining a warmer (photosphere) standard star spectrum with a cooler (spot) standard weighted by the spot filling factor, f _spot . The best-fit models spanned two photospheric component temperatures, T _phot = 4100 K (K7V) and 4400 K (K5V), and one spot component temperature, T _spot = 3060 K (M5V) with an A _V of 0.3. We find values of f _spot to vary between 0.77 and 0.94 with an average uncertainty of ∼0.04. The variability of f _spot is periodic and correlates with its 3.374 day rotational period. Using a mean value for f ^mean _spot to represent the total spot coverage, we calculated spot corrected values for T _eff and L _⋆ . Placing these values alongside evolutionary models developed for heavily spotted young stars, we infer mass and age ranges of 0.45–0.6 M _⊙ and 0.50–1.25 Myr, respectively. These inferred values represent a twofold increase in the mass and a twofold decrease in the age as compared to standard evolutionary models. Such a result highlights the need for constraining the contributions of cool and warm regions of young stellar atmospheres when estimating T _eff and L _⋆ to infer masses and ages as well as the necessity for models to account for the effects of these regions on the early evolution of low-mass stars.https://doi.org/10.3847/1538-4357/acbb61T Tauri starsStar formationEarly stellar evolutionStarspotsPre-main sequence starsStellar evolutionary tracks |
| spellingShingle | Facundo Pérez Paolino Jeffrey S. Bary Michael S. Petersen Kimberly Ward-Duong Benjamin M. Tofflemire Katherine B. Follette Heidi Mach Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4 The Astrophysical Journal T Tauri stars Star formation Early stellar evolution Starspots Pre-main sequence stars Stellar evolutionary tracks |
| title | Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4 |
| title_full | Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4 |
| title_fullStr | Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4 |
| title_full_unstemmed | Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4 |
| title_short | Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4 |
| title_sort | correlating changes in spot filling factors with stellar rotation the case of lkca 4 |
| topic | T Tauri stars Star formation Early stellar evolution Starspots Pre-main sequence stars Stellar evolutionary tracks |
| url | https://doi.org/10.3847/1538-4357/acbb61 |
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