Journal Article

A rival for Babcock's star: the extreme 30-kG variable magnetic field in the Ap star HD 75049*

V. G. Elkin, G. Mathys, D. W. Kurtz, S. Hubrig and L. M. Freyhammer

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 402, issue 3, pages 1883-1891
Published in print March 2010 | ISSN: 0035-8711
Published online February 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.16015.x
A rival for Babcock's star: the extreme 30-kG variable magnetic field in the Ap star HD 75049*

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The extraordinary magnetic Ap star HD 75049 has been studied with data obtained with the European Southern Observatory Very Large Telescope and 2.2-m telescopes. Direct measurements reveal that the magnetic field modulus at maximum reaches 30 kG. The star shows photometric, spectral and magnetic variability with a rotation period of 4.049 d. Variations of the mean longitudinal magnetic field can be described to first order by a centred dipole model with an inclination i= 25°, an obliquity β= 60° and a polar field Bp= 42 kG. The combination of the longitudinal and surface magnetic field measurements implies a radius of R= 1.7 R, suggesting that the star is close to the zero-age main sequence. HD 75049 displays moderate overabundances of Si, Ti, Cr, Fe and large overabundances of rare earth elements. This star has the second strongest magnetic field of any main-sequence star after Babcock's star, HD 215441, which it rivals.

Keywords: stars: chemically peculiar; stars: individual: HD 75049; stars: magnetic fields; stars: variables other

Journal Article.  6182 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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