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The long-term variation of the effective magnetic field of the active star ε Eridani

Published online by Cambridge University Press:  27 November 2018

Cesare Scalia Open the ORCID record for Cesare Scalia [Opens in a new window] ,
Francesco Leone  and
Manuele Gangi
Cesare Scalia
Affiliation:
Università di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Via S. Sofia 78, I–95123 Catania, Italy INAF - Osservatorio Astrofisico di Catania, Via S. Sofia 78, I–95123 Catania, Italy email: cesare.scalia@oact.inaf.it
Francesco Leone
Affiliation:
Università di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Via S. Sofia 78, I–95123 Catania, Italy INAF - Osservatorio Astrofisico di Catania, Via S. Sofia 78, I–95123 Catania, Italy email: cesare.scalia@oact.inaf.it
Manuele Gangi
Affiliation:
Università di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Via S. Sofia 78, I–95123 Catania, Italy INAF - Osservatorio Astrofisico di Catania, Via S. Sofia 78, I–95123 Catania, Italy email: cesare.scalia@oact.inaf.it
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Abstract

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Long-term periodicities of magnetic fields in cool stars are usually studied from activity indicators, which are only indirectly related to the presence of the field. Direct detections are complicated issues since even a complex magnetic structure, as the solar one, has a very low disk integrated magnetic signal, which is usually hidden in the noise level. We introduce a method for the direct measurement of small integrated longitudinal stellar magnetic fields (effective magnetic fields), called multi-line slope method, based on the regression of the Stokes V signal with respect to the first derivative of Stokes I. We present the results of the application of this technique to a dataset of 9 yr of observations of the active star epsilon Eridani, obtained with the spectropolarimeters Narval, HARPSpol and CAOS, showing that the long-term variation of the effective magnetic field corresponds to the period of the cycle retrieved by the activity indicators.

Keywords

stars: late-typestars: magnetic fieldsstars: activitytechniques: polarimetrictechniques: spectroscopicmethods: data analysis
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 13 , Symposium S340: Long-term Datasets for the Understanding of Solar and Stellar Magnetic Cycles , February 2018 , pp. 39 - 42
Copyright
Copyright © International Astronomical Union 2018 

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