E. A. Semenko

Results of magnetic field measurements of CP stars carried out with the Russian 6-m telescope. I. Observations in 2007

This paper presents the results of magnetic field measurements for 39 chemically peculiar and 3 normal main sequence stars used as standard stars. Observations were carried out with the Main Stellar Spectrograph of the Russian 6-m telescope during 2007. Zeeman measurements for 8 stars were performed for the first time. The accuracy analysis for the longitudinal magnetic field measurements of the stars confirms that the systematic errors do not exceed 10–20 G and are within the quoted limits. The absence of significant instrumental deviations follows from the measurements of the CP stars with well-known Be variation curves.

High-resolution fiber-fed echelle spectrograph for the 6-m telescope. I. Optical scheme, arrangement, and control system

We propose a project of a high-resolution (R = 100 000) fiber-fed spectrograph for comprehensive studies of stellar atmospheres, exoplanet searches, asteroseismological studies, studies of stellar magnetism, active nuclei of bright galaxies, interstellar medium, etc. We present the optical scheme of the instrument. The operating wavelength region spans from 4000 to 7500 Å. We also present the optical scheme of the pre-fiber optic unit of the spectrograph. The unit supports four main modes of spectroscopic observations: the mode of traditional spectroscopy with the spectrum of the studied object taken along with the background spectrum in the immediate vicinity of the object; the mode of the simultaneous recording of the spectrum of the object and that of the wavelength standard; the mode of high-precision spectroscopy with an iodine cell, and the mode of spectropolarimetric observations with the measurement of all the Stokes parameters.

Magnetic field monitoring of the very slowly rotating CP star HD 965

With the 6-m telescope we performed the magnetic field Be measurements for the chemically peculiar star HD 965. During 2000–2015 we obtained over 30 spectra with a Zeeman circular polarization analyzer. The longitudinal field reaches +600 G at the positive extremum and goes below −1300 G at the negative one. The magnetic monitoring of the star shows that the period of Be variability, i.e., the rotation period, exceeds 15 years. Thus, HD 965 belongs to the five slowest rotators among magnetic stars.

Chemically peculiar stars in the orion OB1 association. I. occurrence frequency, spatial distribution, and kinematics

A total of 85 CP stars of various types are identified among 814 members of the OriOB1 association. The fraction of CP stars decreases with age for different cluster subgroups: from 15.1% in the youngest subgroup (b) to 7.7% in the oldest one (a). Individual comments are provided for each of the 85 stars, where we analyze the physical parameters and distance of the objects. All the 23 Am stars identified as a result of this study are found to have heliocentric distances between 100 and 300 pc and appear not to be members of the OrionOB1 association, but foreground objects. We identified 59 Bp stars, which account for 13.4% of the total number of B-type stars in the association. The fraction of peculiar B-type stars in the OriOB1 association is found to be twice higher than that of peculiar A-type stars. The same is true for field stars. The association contains 22 magnetic stars, out of which 21 are Bp stars and only one is an Ap star. Seventeen of these stars are objects with anomalous helium lines. Magnetic stars show a well-defined tendency to concentrate in the central region of the association (in Orion’s Belt), which contains most of these objects. No significant differences are found between the field strengths in the B-type stars of the association and Bp-type field stars, although there is a noticeable trend for He-rich stars to have stronger fields compared to He-weak stars. We identified 17 binaries, which make up 20% of the total number of peculiar stars studied, which is the standard ratio for CP stars. Except for one HgMn star (HD35548), the radial velocities and proper motions of our identified objects are consistent with the corresponding parameters of normal B-type stars.

On discovery of strong magnetic field in the binary system HD34736

We present the results of a study of the star HD34736. The spectropolarimetric observations carried out at the 6-m telescope showed the presence of a strong variable longitudinal magnetic field, exceeding −4500 G. The analysis of the Hipparcos photometry gives a set of possible periods of the brightness variability of the star, of which

Stars with discrepant v sin i as derived from Ca II 3933 and Mg II 4481 Å lines. I. Composite-spectrum star HD 2913

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Results of magnetic field measurements of CP-stars performed with the 6-m telescope. III. Observations in 2009

is preferred. The variable radial velocity of spectral lines of the star and some signatures of lines of at least one other component show that HD34736 is a binary short-period system. Modeling of the spectra allowed us to estimate the effective temperature Teff of the stars (13 700 and 11 500 K) and their projected rotational velocities υ sin i (73 and ≥ 90 km s−1). The analysis of all the available information about the star allows us to hypothesize that the object of study is a close, possibly interacting binary system.

Magnetic field of CP stars in the Ori OB1 association. I. HD35456, HD35881, HD36313 A, HD36526

The results of a complex study of the chemically peculiar star HD 45583 are reported. Observations were made using the Main Stellar Spectrograph equipped with a circular polarization analyzer and NES echelle spectrograph of the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. Our measurements of Zeeman spectra show that the star exhibits unusual variations of the longitudinal component of magnetic field with a secondary minimum. The period of spectral and magnetic variability coincides with the rotation period, which is equal to 1.d177000. Two possible causes of the secondary minimum are discussed: spots with higher than ambient content of some chemical elements on the star’s surface or complex structure of the stellar magnetic field. The parameters of the star’s atmosphere are determined (Teff = 13000 K, log g = 4.0), as well as the abundances of some elements: the star shows a 1–2 dex overabundance of Fe, Si, and Cr, helium is underabundant by about 2 dex with respect to the Sun.