The Orbit and Dynamical Mass of Polaris: Observations with the CHARA Array
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Fecha
2024-08
Profesor/a Guía
Facultad/escuela
Idioma
en
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Título del volumen
Editor
Institute of Physics
Nombre de Curso
Licencia CC
CC BY 4.0 Attribution 4.0 International
Licencia CC
https://creativecommons.org/licenses/by/4.0/
Resumen
The 30 yr orbit of the Cepheid Polaris has been followed with observations by the Center for High Angular Resolution Astronomy (CHARA) Array from 2016 through 2021. An additional measurement has been made with speckle interferometry at the Apache Point Observatory. Detection of the companion is complicated by its comparative faintness—an extreme flux ratio. Angular diameter measurements appear to show some variation with pulsation phase. Astrometric positions of the companion were measured with a custom grid-based model-fitting procedure and confirmed with the CANDID software. These positions were combined with the extensive radial velocities (RVs) discussed by Torres to fit an orbit. Because of the imbalance of the sizes of the astrometry and RV data sets, several methods of weighting are discussed. The resulting mass of the Cepheid is 5.13 ± 0.28 M ⊙. Because of the comparatively large eccentricity of the orbit (0.63), the mass derived is sensitive to the value found for the eccentricity. The mass combined with the distance shows that the Cepheid is more luminous than predicted for this mass from evolutionary tracks. The identification of surface spots is discussed. This would give credence to the identification of a radial velocity variation with a period of approximately 120 days as a rotation period. Polaris has some unusual properties (rapid period change, a phase jump, variable amplitude, and unusual polarization). However, a pulsation scenario involving pulsation mode, orbital periastron passage, and low pulsation amplitude can explain these characteristics within the framework of pulsation seen in Cepheids.
Notas
Indexación: Scopus.
Palabras clave
Variable Star, Magellanic Clouds, Photometry
Citación
Astrophysical Journal Open Access Volume 971, Issue 21 August 2024 Article number 190
DOI
10.3847/1538-4357/ad5e7a