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Post Info TOPIC: HgMn stars
Blobrana


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RE: HgMn stars
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Title: Four new HgMn stars: HD 18104, HD 30085, HD 32867, HD 53588
Author: R. Monier, M. Gebran, F. Royer

We have detected four new HgMn stars, while monitoring a sample of apparently slowly rotating superficially normal bright late B and early A stars in the northern hemisphere. Important classification lines of Hg II and Mn II are found as conspicuous features in the high resolution SOPHIE spectra of these stars (R = 75000). Several lines of Hg II, Mn II and Fe II have been synthesized using model atmospheres and the spectrum synthesis code SYNSPEC48 including hyperfine structure of various isotopes when relevant. These synthetic spectra have been compared to high resolution high signal-to-noise observations of these stars in order to derive abundances of these key elements. The four stars are found to have distinct enhancements of Hg and Mn which show that these stars are not superficially normal B and A stars, but actually are new HgMn stars and should reclassified as such.

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Blobrana


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Title: Magnetic fields of HgMn stars
Authors: S. Hubrig, J. F. Gonzalez, I. Ilyin, H. Korhonen, M. Schoeller, I. Savanov, R. Arlt, F. Castelli, G. Lo Curto, M. Briquet, T. H. Dall

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.
We re-analyse 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 HD65949 and the hotter analogue of HgMn stars, the PGa star HD19400, using FORS2 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.
We downloaded from the ESO archive the publicly available HARPS spectra for eight HgMn stars and one normal and one superficially normal B-type star obtained in 2010. 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 HD65949 and the PGa star HD19400 are based on a linear regression analysis of low-resolution spectra obtained with FORS2 in spectropolarimetric mode.
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.

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Blobrana


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Posts: 131433
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Title: Spots on the surface of HgMn stars: Clues to the origin of Hg and Mn peculiarities
Authors: S. Hubrig, J.F. Gonzalez, R. Arlt

The important result achieved in our recent study of a large sample of HgMn stars using UVES at the VLT and FEROS at the ESO 2.2m telescope is the finding that most HgMn stars exhibit spectral variability of various chemical elements, proving that the presence of an inhomogeneous distribution on the surface of these stars is a rather common characteristics and not a rare phenomenon.

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