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Astron. Astrophys. 325, 195-202

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Discovery of a very large magnetic field in three Ap stars*

J. Babel1 and P. North2

1Institut für Astronomie und Astrophysik, Universität Kiel, D-24098 Kiel, Germany (babel@astrophysik.uni-kiel.de)
2Institut d'Astronomie de l'Université de Lausanne, CH-1290 Chavannes-des-Bois, Switzerland (Pierre.North@obs.unige.ch)

Received 12 December 1996 / Accepted 13 March 1997


We report the discovery of magnetic fields larger than 11 kG in the three Ap SrCrEu stars BD FORMULA , HD 63843 and HD 86592. In addition, we give new results for the star HD 47103, where the correlation peak is resolved into magnetically split components.

The average (quadratic) surface field measured by correlation methods in the three newly measured stars is 16, 12 and 16 kG respectively. Their effective temperatures, estimated from the profile of the Balmer lines, are 7100, 7500 and 7600 K. The projected rotational velocities are 17, <5 and 16 km s-1 respectively, so that two of these objects are not extremely slow rotators. One object, BD FORMULA , is particularly interesting as it undergoes a strong variation of the magnetic field on a timescale of days with extreme values at 12.8 and 22 kG, together with a large variation of the radial velocity measured in H FORMULA and H FORMULA indicating a probable close SB1 system. For HD 86592, a period P = 2.887 days is also determined from Geneva photometry.

Our new measurements of HD 47103 do not show any relative variation of <H> larger than FORMULA compared with those of April 1995, suggesting that the rotational period of this star might be very long, of the order of years. It shows, however, a significant shift in vrad indicating a membership in a binary system

Key words: stars: individual: HD 47103, HD 63843,
HD 86592 - stars: chemically peculiar - stars: magnetic fields - line: profiles

*Based on observations collected at the Observatoire de Haute-Provence (OHP), France

Send offprint requests to: J. Babel

© European Southern Observatory (ESO) 1997