ICATE   21876
INSTITUTO DE CIENCIAS ASTRONOMICAS, DE LA TIERRA Y DEL ESPACIO
Unidad Ejecutora - UE
artículos
Título:
Magnetic fields of HgMn stars
Autor/es:
HUBRIG, S.; GONZÁLEZ, J.F.; ILYIN, I.; KORHONEN, H.; SCHÖLLER, M.; SAVANOV, I.; ARLT, R.; CASTELLI, F.; LO CURTO, G.; BRIQUET, M.; DALL, T. H.
Revista:
ASTRONOMY AND ASTROPHYSICS
Editorial:
EDP SCIENCES S A
Referencias:
Lugar: Paris; Año: 2012 vol. 547 p. 1 - 24
ISSN:
0004-6361
Resumen:
Context. The frequent presence of weak magnetic fields on the surface of
spotted late-B stars with HgMn peculiarity in binary systems has been
controversial during the two last decades. Recent studies of magnetic
fields in these stars using the least-squares deconvolution (LSD)
technique have failed to detect magnetic fields, indicating an upper
limit on the longitudinal field between 8 and 15 G. In these LSD
studies, assumptions were made that all spectral lines are identical in
shape and can be described by a scaled mean profile. Aims: We
re-analyse the available spectropolarimetric material by applying the
moment technique on spectral lines of inhomogeneously distributed
elements separately. Furthermore, we present new determinations of the
mean longitudinal magnetic field for the HgMn star HD 65949 and the
hotter analog of HgMn stars, the PGa star HD 19400, using FORS 2
installed at the VLT. We also give new measurements of the eclipsing
system AR Aur with a primary star of HgMn peculiarity, which were
obtained with the SOFIN spectropolarimeter installed at the Nordic
Optical Telescope. Methods: We downloaded from the European
Southern Observatory (ESO) archive the publically available HARPS
spectra for eight HgMn stars and one normal and one superficially normal
B-type star obtained in 2010. Out of this sample, three HgMn stars
belong to spectroscopic double-lined systems. The application of the
moment technique to the HARPS and SOFIN spectra allowed us to study the
presence of the longitudinal magnetic field, the crossover effect, and
quadratic magnetic fields. Results for the HgMn star HD 65949 and the
PGa star HD 19400 are based on a linear regression analysis of
low-resolution spectra obtained with FORS 2 in spectropolarimetric mode.
Results: Our measurements of the magnetic field with the moment
technique using spectral lines of several elements separately reveal the
presence of a weak longitudinal magnetic field, a quadratic magnetic
field, and the crossover effect on the surface of several HgMn stars as
well as normal and superficially normal B-type stars. Furthermore, our
analysis suggests the existence of intriguing correlations between the
strength of the magnetic field, abundance anomalies, and binary
properties. The results are discussed in the context of possible
mechanisms responsible for the development of the element patches and
complex magnetic fields on the surface of late B-type stars.