Letter to the Editor

Discovery of the pre-main sequence progenitors of the magnetic Ap/Bp stars?

¹ Dept. of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston, Canada, K7K 4B4 e-mail: Gregg.Wade@rmc.ca
² European Southern Observatory, Casilla 19001, Santiago 19, Chile
³ Dept. of Physics & Astronomy, University of Western Ontario, London, Canada, N6A 3K7
⁴ Department of Physics, Queen's University, Kingston, Canada
⁵ Obs. de Paris LESIA, 5 place Jules Janssen, 92195 Meudon Cedex, France
⁶ Obs. Midi-Pyrénées, 14 avenue Edouard Belin, Toulouse, France
⁷ Laboratoire d'Astrophysique de Marseille, Traverse du Siphon, BP 8, 13376 Marseille Cedex 12, France

Received: 25 May 2005
Accepted: 11 September 2005

Abstract

We report the discovery, using FORS1 at the ESO-VLT and ESPaDOnS at the CFHT, of magnetic fields in the young A-type stars HD 101412, V380 Ori and HD 72106A. Two of these stars (HD 101412 and V380 Ori) are pre-main sequence Herbig Ae/Be (HAeBe) stars, while one (HD 72106A) is physically associated with a HAeBe star. Remarkably, evidence of surface abundance spots is detected in the spectra of HD 72106A. The magnetic fields of these objects display intensities of order 1 kG at the photospheric level, are ordered on global scales, and appear in approximately 10% of the stars studied. Based on these properties, the detected stars may well represent pre-main sequence progenitors of the magnetic Ap/Bp stars. The low masses inferred for these objects (2.6, 2.8 and 2.4 ) represent additional contradictions to the hypothesis of Hubrig et al. (2000, ApJ, 539, 352), who claim that magnetic fields appear in intermediate-mass stars only after 30% of their main sequence evolution is complete. Finally, we fail to confirm claims by Hubrig et al. (2004, A&A, 428, L1) of magnetic fields in the Herbig Ae star HD 139614.