Magnetic fields and differential rotation on the pre-main sequence - I. The early-G star HD 141943 - brightness and magnetic topologies

Marsden, S. C. and Jardine, M. M. and Ramirez Velez, J. C. and Alecian, E. and Brown, C. J. and Carter, B. D. and Donati, J.-F. and Dunstone, N. and Hart, R. and Semel, M. and Waite, I. A. (2011) Magnetic fields and differential rotation on the pre-main sequence - I. The early-G star HD 141943 - brightness and magnetic topologies. Monthly Notices of the Royal Astronomical Society, 413 (3). pp. 1922-1938. ISSN 0035-8711

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Abstract

Spectroscopic and spectropolarimetric observations of the pre-main sequence early-G star HD 141943 were obtained at four observing epochs (in 2006, 2007, 2009 and 2010). The observations were undertaken at the 3.9-m Anglo-Australian Telescope using the UCLES echelle spectrograph and the SEMPOL spectropolarimeter visitor instrument. Brightness and surface magnetic field topologies were reconstructed for the star using the technique of least-squares deconvolution to increase the signal-to-noise ratio of the data. The reconstructed brightness maps show that HD 141943 had a weak polar spot and a significant amount of low-latitude features, with little change in the latitude distribution of the spots over the 4 yr of observations. The surface magnetic field was reconstructed at three of the epochs from a high-order (l≤ 30) spherical harmonic expansion of the spectropolarimetric observations. The reconstructed magnetic topologies show that in 2007 and 2010 the surface magnetic field was reasonably balanced between poloidal and toroidal components. However, we find tentative evidence of a change in the poloidal/toroidal ratio in 2009 with the poloidal component becoming more dominant. At all epochs the radial magnetic field is predominantly non-axisymmetric while the azimuthal field is predominantly axisymmetric with a ring of positive azimuthal field around the pole similar to that seen on other active stars.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Authors retain copyright over content; Publisher retains copyright over presentation. Author version made available.
Depositing User: Dr Brad Carter
Faculty / Department / School: Historic - Faculty of Sciences - Department of Biological and Physical Sciences
Date Deposited: 24 Mar 2012 08:17
Last Modified: 11 Oct 2013 01:35
Uncontrolled Keywords: star activity; imaging; magnetic fields; individual stars; HD 141943
Fields of Research (FOR2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
02 Physical Sciences > 0205 Optical Physics > 020503 Nonlinear Optics and Spectroscopy
01 Mathematical Sciences > 0101 Pure Mathematics > 010112 Topology
Socio-Economic Objective (SEO2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: doi: 10.1111/j.1365-2966.2011.18367.x
URI: http://eprints.usq.edu.au/id/eprint/20478

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