Volume 574, February 2015
|Number of page(s)||18|
|Published online||19 January 2015|
The case of AF Leporis
Leibniz-Institut für Astrophysik Potsdam,
An der Sternwarte 16,
2 Department of Physics, University of Helsinki, PO Box 64, 00014 Helsinki, Finland
3 Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
4 Computational Engineering and Science Research Centre, University of Southern Queensland, 4350 Toowoomba, Australia
5 Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, 79104 Freiburg, Germany
Received: 19 May 2014
Accepted: 3 November 2014
Context. The (Zeeman-)Doppler imaging studies of solar-type stars very often reveal large high-latitude spots. This also includes F stars that possess relatively shallow convection zones, indicating that the dynamo operating in these stars differs from the solar dynamo.
Aims. We aim to determine whether mean-field dynamo models of late-F type dwarf stars can reproduce the surface features recovered in Doppler maps. In particular, we wish to test whether the models can reproduce the high-latitude spots observed on some F dwarfs.
Methods. The photometric inversions and the surface temperature maps of AF Lep were obtained using the Occamian-approach inversion technique. Low signal-to-noise spectroscopic data were improved by applying the least-squares deconvolution method. The locations of strong magnetic flux in the stellar tachocline as well as the surface fields obtained from mean-field dynamo solutions were compared with the observed surface temperature maps.
Results. The photometric record of AF Lep reveals both long- and short-term variability. However, the current data set is too short for cycle-length estimates. From the photometry, we have determined the rotation period of the star to be 0.9660 ± 0.0023 days. The surface temperature maps show a dominant, but evolving, high-latitude (around +65°) spot. Detailed study of the photometry reveals that sometimes the spot coverage varies only marginally over a long time, and at other times it varies rapidly. Of a suite of dynamo models, the model with a radiative interior rotating as fast as the convection zone at the equator delivered the highest compatibility with the obtained Doppler images.
Key words: stars: imaging / stars: activity / starspots / stars: individual: AF Leb / dynamo
Partially based on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofísica de Canarias.
Tables 1–3 and Figs. 7–14 are available in electronic form at http://www.aanda.org
© ESO, 2015
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