The relation between stellar magnetic field geometry and chromospheric activity cycles - I. The highly variable field of Eps Eridani at activity minimum

Jeffers, S. V. and Boro Saikia, S. and Barnes, J. R. and Petit, P. and Marsden, S. C. and Jardine, M. M. and Vidotto, A. A. (2017) The relation between stellar magnetic field geometry and chromospheric activity cycles - I. The highly variable field of Eps Eridani at activity minimum. Monthly Notices of the Royal Astronomical Society: Letters, 471 (1). L96-L100. ISSN 0035-8711

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Abstract

The young and magnetically active K dwarf eps Eridani exhibits a chromospheric activity cycle of about 3 yr. Previous reconstructions of its large-scale magnetic field show strong variations at yearly epochs. To understand how eps Eridani’s large-scale magnetic field geometry evolves over its activity cycle, we focus on high-cadence observations spanning 5 months at its activity minimum. Over this time-span, we reconstruct three maps of eps Eridani’s large-scale magnetic field using the tomographic technique of Zeeman–Doppler imaging. The results show that at the minimum of its cycle, eps Eridani’s large-scale field is more complex than the simple dipolar structure of the Sun and 61 Cyg A at minimum. Additionally, we observe a surprisingly rapid regeneration of a strong axisymmetric toroidal field as eps Eridani emerges from its S-index
activity minimum. Our results show that all stars do not exhibit the same field geometry as the Sun, and this will be an important constraint for the dynamo models of active solar-type stars.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Access to Published version in accordance with the copyright policy of the publisher.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences
Date Deposited: 21 Jan 2018 23:28
Last Modified: 08 May 2018 00:11
Uncontrolled Keywords: polarimetric, stars, eps Eridani, magnetic field, solar-type
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: 10.1093/mnrasl/slx097
URI: http://eprints.usq.edu.au/id/eprint/33565

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