Measuring stellar differential rotation with high-precision space-borne photometry

Context. Stellar differential rotation is important for understanding hydromagnetic stellar dynamos, instabilities, and transport processes in stellar interiors, as well as for a better treatment of tides in close binary and star-planet systems. Aims. We introduce a method of measuring a lower limit...

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Principais autores: Lanza, A. F., Chagas, M. L. das, Medeiros, José Renan de
Formato: article
Idioma:English
Publicado em: EDP Sciences
Assuntos:
Sun: rotation
Stars: rotation
Stars: late-type
Starspots
Endereço do item:https://repositorio.ufrn.br/jspui/handle/123456789/29024
https://doi.org/10.1051/0004-6361/201323172
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spelling ri-123456789-290242020-05-24T09:21:17Z Measuring stellar differential rotation with high-precision space-borne photometry Lanza, A. F. Chagas, M. L. das Medeiros, José Renan de Sun: rotation Stars: rotation Stars: late-type Starspots Context. Stellar differential rotation is important for understanding hydromagnetic stellar dynamos, instabilities, and transport processes in stellar interiors, as well as for a better treatment of tides in close binary and star-planet systems. Aims. We introduce a method of measuring a lower limit to the amplitude of surface differential rotation from high-precision, evenly sampled photometric time series, such as those obtained by space-borne telescopes. It is designed to be applied to main-sequence late-type stars whose optical flux modulation is dominated by starspots. Methods. An autocorrelation of the time series was used to select stars that allow an accurate determination of starspot rotation periods. A simple two-spot model was applied together with a Bayesian information criterion to preliminarily select intervals of the time series showing evidence of differential rotation with starspots of almost constant area. Finally, the significance of the differential rotation detection and a measurement of its amplitude and uncertainty were obtained by an a posteriori Bayesian analysis based on a Monte Carlo Markov chain approach. We applied our method to the Sun and eight other stars for which previous spot modelling had been performed to compare our results with previous ones. Results. We find that autocorrelation is a simple method for selecting stars with a coherent rotational signal that is a prerequisite for successfully measuring differential rotation through spot modelling. For a proper Monte Carlo Markov chain analysis, it is necessary to take the strong correlations among different parameters that exist in spot modelling into account. For the planet-hosting star Kepler-30, we derive a lower limit to the relative amplitude of the differential rotation of ΔP/P = 0.0523±0.0016. We confirm that the Sun as a star in the optical passband is not suitable for measuring differential rotation owing to the rapid evolution of its photospheric active regions. In general, our method performs well in comparison to more sophisticated and time-consuming approaches. 2020-05-19T22:28:33Z 2020-05-19T22:28:33Z 2014 article LANZA, A. F.; CHAGAS, M. L das; MEDEIROS, José Renan de. Measuring stellar differential rotation with high-precision space-borne photometry. Astronomy & Astrophysics (Berlin. Print), v. 564, p. A50-65, 2014. ISSN 1432-0746 versão online. DOI https://doi.org/10.1051/0004-6361/201323172. Disponível em: https://www.aanda.org/articles/aa/abs/2014/04/aa23172-13/aa23172-13.html. Acesso em: 19 maio 2020. Reproduzido com permissão da Astronomy & Astrophysics, © ESO. 0004-6361 (print), 1432-0746 (online) https://repositorio.ufrn.br/jspui/handle/123456789/29024 https://doi.org/10.1051/0004-6361/201323172 en application/pdf EDP Sciences
institution Repositório Institucional
collection RI - UFRN
language English
topic Sun: rotation
Stars: rotation
Stars: late-type
Starspots
spellingShingle Sun: rotation
Stars: rotation
Stars: late-type
Starspots
Lanza, A. F.
Chagas, M. L. das
Medeiros, José Renan de
Measuring stellar differential rotation with high-precision space-borne photometry
description Context. Stellar differential rotation is important for understanding hydromagnetic stellar dynamos, instabilities, and transport processes in stellar interiors, as well as for a better treatment of tides in close binary and star-planet systems. Aims. We introduce a method of measuring a lower limit to the amplitude of surface differential rotation from high-precision, evenly sampled photometric time series, such as those obtained by space-borne telescopes. It is designed to be applied to main-sequence late-type stars whose optical flux modulation is dominated by starspots. Methods. An autocorrelation of the time series was used to select stars that allow an accurate determination of starspot rotation periods. A simple two-spot model was applied together with a Bayesian information criterion to preliminarily select intervals of the time series showing evidence of differential rotation with starspots of almost constant area. Finally, the significance of the differential rotation detection and a measurement of its amplitude and uncertainty were obtained by an a posteriori Bayesian analysis based on a Monte Carlo Markov chain approach. We applied our method to the Sun and eight other stars for which previous spot modelling had been performed to compare our results with previous ones. Results. We find that autocorrelation is a simple method for selecting stars with a coherent rotational signal that is a prerequisite for successfully measuring differential rotation through spot modelling. For a proper Monte Carlo Markov chain analysis, it is necessary to take the strong correlations among different parameters that exist in spot modelling into account. For the planet-hosting star Kepler-30, we derive a lower limit to the relative amplitude of the differential rotation of ΔP/P = 0.0523±0.0016. We confirm that the Sun as a star in the optical passband is not suitable for measuring differential rotation owing to the rapid evolution of its photospheric active regions. In general, our method performs well in comparison to more sophisticated and time-consuming approaches.
format article
author Lanza, A. F.
Chagas, M. L. das
Medeiros, José Renan de
author_facet Lanza, A. F.
Chagas, M. L. das
Medeiros, José Renan de
author_sort Lanza, A. F.
title Measuring stellar differential rotation with high-precision space-borne photometry
title_short Measuring stellar differential rotation with high-precision space-borne photometry
title_full Measuring stellar differential rotation with high-precision space-borne photometry
title_fullStr Measuring stellar differential rotation with high-precision space-borne photometry
title_full_unstemmed Measuring stellar differential rotation with high-precision space-borne photometry
title_sort measuring stellar differential rotation with high-precision space-borne photometry
publisher EDP Sciences
publishDate 2020
url https://repositorio.ufrn.br/jspui/handle/123456789/29024
https://doi.org/10.1051/0004-6361/201323172
work_keys_str_mv AT lanzaaf measuringstellardifferentialrotationwithhighprecisionspacebornephotometry
AT chagasmldas measuringstellardifferentialrotationwithhighprecisionspacebornephotometry
AT medeirosjoserenande measuringstellardifferentialrotationwithhighprecisionspacebornephotometry
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