
TY  - JOUR
A1  - Budding, E. 
A1  - Carter, B. D. 
A1  - Mengel, M. W. 
A1  - Slee, O. B. 
A1  - Donati, J.-F. 
T1  - A Radio and Optical Study of the Active Young F Star HR 1817 (=HD 35850)
JF  - Publications of the Astronomical Society of Australia
JO  - Publ. Astron. Soc.  Aust.
Y1  - 2002
VL  - 19
IS  - 4
SP  - 527
EP  - 533
KW  - Keywords: stars: activity &#8212; stars: coronae &#8212; stars: individual (HR&#32;1817) &#8212; radio continuum: stars &#8212; techniques: miscellaneous &#8212; techniques: Zeeman Doppler imaging
UR  - https://doi.org/10.1071/AS02021 
N2  - This paper presents the results of a multiwavelength observational study of the active young F-type star HR&#32;1817. The star was monitored at 4.80 and 8.64&#32;GHz over 2&#32;&#215;&#32;12&#32;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&#32;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&#32;1817. Comparison of the emissions from 4.80 and 8.64&#32;GHz shows a very strong cross-correlation peak, indicative of a common origin, although the shift of this peak indicates that 8.64&#32;GHz variations tend to precede those at 4.80&#32;GHz by, typically, &#126;20&#32;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&#32;1817 the star with the earliest spectral type on which dynamo magnetic fields have been detected directly up to now. 
ER  -

