2001A&A...375..963H

We suggested in a previous paper that three HgMn stars, HD 175640, HD 178065, and HD 186122, may be suspected to possess a magnetic field that could be larger than 2 kG. We report here new observations of these three stars, three more HgMn stars, and four normal late B-type stars. The search was carried out by measuring the equivalent width of the Fe II λ6147.7Å line relative to the equivalent width of the Fe II λ6149.2Å line. The observed relative differences between the equivalent widths of these Fe II lines are compared with those derived from synthetic spectra computed by neglecting magnetic field effects. To investigate the effect of oscillator strength uncertainties on the results, we computed equivalent widths by using both Fe II log gf-values taken from Kurucz & Bell (1995, Atomic Line List, CD-ROM No. 23, Smithonian Astrophys. Obs. (Cambridge, MA)) and Fe II log gf-values taken from Raassen & Uylings (2000, The atomic data on the Web, http://www.science.uva.nl/pub/orth/iron/FeII.E1 ). The comparison of the computed and observed equivalent widths based on the Kurucz & Bell (1995) atomic data leads us to conclude that all the stars of our sample, except HD 175640, are very likely to possess a magnetic field. On the other hand, the comparison of the computed and observed equivalent widths based on the Raassen & Uylings (2000, The atomic data on the Web, http://www.science.uva.nl/pub/orth/iron/FeII.E1 ) log gf-values suggests the possible presence of magnetic fields only in three stars, the HgMn star HD 16717 and the two normal B-type stars HD 179761 and HD 186568. The latter two are those in the sample with the largest vsini (15km/s and 18km/s, respectively), so that the results for them are the most uncertain ones.