Activity and magnetic field structure of the Sun-like planet-hosting star HD 1237

¹ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
e-mail: jalvarad@eso.org
² Universitäts-Sternwarte München, Ludwig-Maximilians-Universität, Scheinerstr. 1, 81679 München, Germany
³ INAF–Osservatorio Astrofisico di Catania, via Santa Sofia 87, 95123 Catania, Italy
⁴ Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, UPS-OMP, 31400 Toulouse, France
⁵ CNRS, Institut de Recherche en Astrophysique et Planétologie, 14 avenue Edouard Belin, 31400 Toulouse, France
⁶ UJF Grenoble 1 CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, France
⁷ LESIA, Observatoire de Paris, CNRS UMR 8109, UPMC, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
⁸ Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
⁹ LUPM-UMR 5299, CNRS & Université Montpellier, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France
¹⁰ Astronomy Department, Van Vleck Observatory, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459, USA
¹¹ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
¹² SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS, UK
¹³ Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4SB, UK
¹⁴ Department of Physics and Astronomy, Stony Brook University, Stony Brook NY 11794-3800, USA

Received: 30 January 2015
Accepted: 13 July 2015

Abstract

We analyse the magnetic activity characteristics of the planet-hosting Sun-like star, HD 1237, using HARPS spectro-polarimetric time-series data. We find evidence of rotational modulation of the magnetic longitudinal field measurements that is consistent with our ZDI analysis with a period of 7 days. We investigate the effect of customising the LSD mask to the line depths of the observed spectrum and find that it has a minimal effect on the shape of the extracted Stokes V profile but does result in a small increase in the S/N (~7%). We find that using a Milne-Eddington solution to describe the local line profile provides a better fit to the LSD profiles in this slowly rotating star, which also affects the recovered ZDI field distribution. We also introduce a fit-stopping criterion based on the information content (entropy) of the ZDI map solution set. The recovered magnetic field maps show a strong (+90 G) ring-like azimuthal field distribution and a complex radial field dominating at mid latitudes (~45 degrees). Similar magnetic field maps are recovered from data acquired five months apart. Future work will investigate how this surface magnetic field distribution affeccts the coronal magnetic field and extended environment around this planet-hosting star.