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A Radio and Optical Study of the Active Young F Star HR 1817 (=HD 35850)

Published online by Cambridge University Press:  05 March 2013

E. Budding ,
B. D. Carter ,
M. W. Mengel ,
O. B. Slee  and
J.-F. Donati
E. Budding
Affiliation:
Central Institute of Technology, PO Box 40740, Wellington, New Zealand. Carter Observatory, PO Box 2909, Wellington, New Zealand
B. D. Carter
Affiliation:
Centre for Astronomy, Solar Radiation and Climate, Faculty of Sciences, University of Southern Queensland, Toowoomba, Queensland 4350, Australia; carterb@usq.edu.au
M. W. Mengel
Affiliation:
Centre for Astronomy, Solar Radiation and Climate, Faculty of Sciences, University of Southern Queensland, Toowoomba, Queensland 4350, Australia; mengelm@usq.edu.au
O. B. Slee
Affiliation:
Australia Telescope National Facility, PO Box 76, Epping, NSW 1710, Australia; Bruce.Slee@atnf.csiro.au
J.-F. Donati
Affiliation:
Observatoire Midi-Pyrénées, 14 avenue Edouard Belin, F-31400 Toulouse, France; jean-francois.donati@ast.obs-mip.fr
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Abstract

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This paper presents the results of a multiwavelength observational study of the active young F-type star HR 1817. The star was monitored at 4.80 and 8.64 GHz over 2 × 12 h allocations with the Australia Telescope Compact Array on 8 and 9 December, 2000. The Anglo-Australian Telescope was used for simultaneous optical spectropolarimetry during a 2 h period on 9 December.

The low levels of observed radio emission have characteristics that are similar to those seen in other active stars, and a gyrosynchrotron mechanism is proposed to explain them; this is supported by the relatively low fractions of circular polarisation measured in HR 1817.

Comparison of the emissions from 4.80 and 8.64 GHz shows a very strong cross-correlation peak, indicative of a common origin, although the shift of this peak indicates that 8.64 GHz variations tend to precede those at 4.80 GHz by, typically, ˜20 min.

The optical spectropolarimetry reveals polarisation signals characteristic of surface magnetic fields, with profile changes indicating a complex dynamo-type magnetic topology is present on the star. This result makes HR 1817 the star with the earliest spectral type on which dynamo magnetic fields have been detected directly up to now.

Keywords

stars: activitystars: coronaestars: individual (HR 1817)radio continuum: starstechniques: miscellaneoustechniques: Zeeman Doppler imaging
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 19 , Issue 4 , 2002 , pp. 527 - 533
Copyright
Copyright © Astronomical Society of Australia 2002

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