Volume 549, January 2013
|Number of page(s)||4|
|Published online||15 January 2013|
The dramatic change of the fossil magnetic field of HD 190073: evidence of the birth of the convective core in a Herbig star?⋆
LESIA-Observatoire de Paris, CNRS, UPMC Univ., Univ. Paris-Diderot,
5 place Jules
Meudon Principal Cedex
2 Laboratoire AIM, CEA/DSM, CNRS, Université Paris Diderot, IRFU/SAp Centre de Saclay, 91191 Gif-sur-Yvette, France
3 Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
4 Armagh Observatory, College Hill, Armagh, BT61 9DG, UK
5 Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, N6A 3K7, Canada
Received: 27 November 2012
Accepted: 17 December 2012
In the context of the ESPaDOnS and Narval spectropolarimetric surveys of Herbig Ae/Be stars, we discovered and then monitored the magnetic field of HD 190073 over more than four years, from 2004 to 2009. Our observations all displayed similar Zeeman signatures in the Stokes V spectra, indicating that HD 190073 hosted an aligned dipole, stable over many years, consistent with a fossil origin. We obtained new observations of the star in 2011 and 2012 and detected clear variations of the Zeeman signature on timescales of days to weeks, indicating that the configuration of its field has changed between 2009 and 2011. Such a sudden change of external structure of a fossil field has never previously been observed in any intermediate or high-mass star. HD 190073 is an almost entirely radiative pre-main sequence star, probably hosting a growing convective core. We propose that this dramatic change is the result of the interaction between the fossil field and the ignition of a dynamo field generated in the newly-born convective core.
Key words: stars: early-type / stars: pre-main sequence / stars: magnetic field / stars: evolution / stars: individual: HD 190073
Based on observations collected at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l’Univers (INSU) of the Centre National de la Recherche Scientifique (CNRS) of France and the University of Hawaii, at the Observatoire du Pic du Midi (France), operated by INSU, and at the European Southern Observatory, Chile (Program ID 187.D-0917).
© ESO, 2013
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