We discuss most recent spectroscopic and spectropolarimetric observations of the star HD 19400 representative of the group of PGa stars. Our high-spectral-resolution study of abundances, line profile variability, and the longitudinal magnetic field o
f HD 19400 discloses a remarkable similarity between this group and the group of HgMn stars.
BG Gem is an eclipsing binary with a 91.6-day orbital period. The more massive primary component does not seem to show absorption lines in the spectrum, while the less massive secondary is thought to be a K-type star, possibly a supergiant. These res
ults were obtained with optical low-resolution spectroscopy and photometry. The primary was suggested to be a black hole, although with a low confidence. We present a high-resolution optical spectrum of the system along with new BVR-photometry. Analysis of the spectrum shows that the K-type star rotates rapidly at v sin i = 18 km/s compared to most evolved stars of this temperature range. We also discuss constraints on the secondarys luminosity using spectroscopic criteria and on the entire system parameters using both the spectrum and photometry.
Context: Open clusters are very useful targets for examining possible trends in galactocentric distance and age, especially when young and old open clusters are compared. Aims: We carried out a detailed spectroscopic analysis to derive the chemical c
omposition of seven red giants in the young open cluster NGC 3114. Abundances of C, N, O, Li, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd were obtained, as well as the carbon isotopic ratio. Methods: The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employed the local-thermodynamic-equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. The abundances of the light elements were derived using the spectral synthesis technique. Results: We found that NGC 3114 has a mean metallicity of [Fe/H] = -0.01+/-0.03. The isochrone fit yielded a turn-off mass of 4.2 Msun. The [N/C] ratio is in good agreement with the models predicted by first dredge-up. We found that two stars, HD 87479 and HD 304864, have high rotational velocities of 15.0 km/s and 11.0 km/s; HD 87526 is a halo star and is not a member of NGC 3114. Conclusions: The carbon and nitrogen abundance in NGC 3114 agree with the field and cluster giants. The oxygen abundance in NGC 3114 is lower compared to the field giants. The [O/Fe] ratio is similar to the giants in young clusters. We detected sodium enrichment in the analyzed cluster giants. As far as the other elements are concerned, their [X/Fe] ratios follow the same trend seen in giants with the same metallicity.
Based on an analysis of the catalog of magnetic fields, we have investigated the statistical properties of the mean magnetic fields for OB stars. We show that the mean effective magnetic field ${cal B}$ of a star can be used as a statistically signif
icant characteristic of its magnetic field. No correlation has been found between the mean magnetic field strength ${cal B}$ and projected rotational velocity of OB stars, which is consistent with the hypothesis about a fossil origin of the magnetic field. We have constructed the magnetic field distribution function for B stars, $F({cal B})$, that has a power-law dependence on ${cal B}$ with an exponent of $approx -1.82$. We have found a sharp decrease in the function $F({cal B})$F for ${cal B}lem 400 G$ that may be related to rapid dissipation of weak stellar surface magnetic fields.
