Is the primary CoRoT target HD 43587 under a Maunder minimum phase?
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Universidade Federal de Minas Gerais
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Artigo de periódico
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CONTEXT. One of the most enigmatic phenomena related to solar activity is the so-called Maunder minimum phase. It consists in
the lowest sunspot count ever registered for the Sun and has not been confirmed for other stars to date. Since the spectroscopic
observations of stellar activity at the Mount Wilson Observatory, the solar analog HD 43587 has shown a very low and apparently
invariant activity level, which makes it a Maunder minimum candidate.
AIMS. We aim to analyze the chromospheric activity evolution of HD 43587 and its evolutive status, with the intention of unraveling
the reasons for this low and flat activity.
METHODS. We used an activity measurements dataset available in the literature, and computed the S -index from HARPS and NARVAL
spectra to infer a cycle period. Additionally, we analyzed the CoRoT light curve of HD 43587, and applied gyrochronology and activity
calibrations to determine its rotation period. Finally, based on an evolutionary model and the inferred rotation period, we used the
EULAG-MHD code to perform global MHD simulations of HD 43587 to get some insight into its dynamo process.
RESULTS. We confirm the almost flat activity profile, with a cycle period Pcyc = 10.44 ± 3.03 yr deduced from the S -index time series,
and a long-term trend that might be a period of more than 50 yr. It was impossible to define a rotation period from the light curve,
however gyrochronology and activity calibrations allow us to infer an indirect estimate of Prot = 22.6 ± 1.9 d. Furthermore, the MHD
simulations confirm an oscillatory dynamo with a cycle period in good agreement with the observations and a low level of surface
magnetic activity.
CONCLUSIONS. We conclude that this object might be experiencing a “natural” decrease in magnetic activity as a consequence of its
age. Nevertheless, the possibility that HD 43587 is in a Maunder minimum phase cannot be ruled out.
Abstract
Assunto
Estrelas, Campos magnéticos
Palavras-chave
Stars, Rotation, Magnetic field
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Endereço externo
https://www.aanda.org/articles/aa/abs/2020/08/aa37219-19/aa37219-19.html