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Astron. Astrophys. 346, 139-145 (1999)

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Search for magnetic fields in HgMn stars by using relative strengths of multiplet 74 Fe II lines *

S. Hubrig 1, F. Castelli 2 and G.M. Wahlgren 3

1 University of Potsdam, Am Neuen Palais 10, D-14469 Potsdam, Germany
2 CNR-Gruppo Nazionale Astronomia and Osservatorio Astronomico, Unita di Ricerca di Trieste, Via G.B. Tiepolo 11, Trieste, Italy
3 Atomic Spectroscopy, Department of Physics, Lund University, Sölvegatan 14, S-223 62, Lund, Sweden

Received 18 January 1999 / Accepted 26 March 1999


The anomalous strength of the Fe  II [FORMULA] line relative to Fe  II [FORMULA] in the stars with magnetic fields is used for detecting magnetic fields in very slowly rotating HgMn stars. The diagnosis based on this pair of magnetically sensitive Fe lines is a simple and fast tool, but its application to more rapidly rotating HgMn stars is hampered by blending with Hg  II [FORMULA]. For spectra of sharp-lined HgMn stars (with [FORMULA] km s-1) taken at high resolving power (R[FORMULA] [FORMULA]) both lines, Fe  II [FORMULA] and Hg  II [FORMULA], become fully unblended. The observed relative differences between the equivalent widths of the two Fe  II lines are compared with those derived from synthetic spectra computed by neglecting magnetic field effects. This comparison has shown that three HgMn stars, HD 175640, HD 178065 and HD 186122 are very likely to possess a magnetic field that could be larger than 2 kG.

Key words: stars: abundances – stars: atmospheres – stars: chemically peculiar – stars: magnetic fields

* Based on observations obtained at the European Southern Observatory, La Silla, Chile (ESO programme No. 61.D-0480)

Send offprint requests to: S. Hubrig

© European Southern Observatory (ESO) 1999

Online publication: May 6, 1999