Gazinur A. Galazutdinov

Narrow Diffuse Interstellar Bands: A Survey with Precise Wavelengths

We present an atlas of 271 diffuse interstellar bands (DIBs) between 4460 and 8800 A based on echelle spectra (R = 45,000), of which more than 100 are new DIBs discovered in this survey. The atlas is restricted mostly to narrow features, and we describe the tests for an interstellar origin. The rest wavelength of each DIB was determined in a high-quality composite spectrum of the star HD 23180 using the interstellar Na i (D1 and D2) lines to establish the radial velocity of the single intervening cloud. DIB wavelengths are quoted to 0.01 A and are probably accurate to ~0.1 A. Other, weak DIBs found in the spectra of heavily reddened stars are included with a lower wavelength precision.

Centrosymmetric molecules as possible carriers of diffuse interstellar bands

In this paper, we present new data with interstellar C 2 (Phillips bands A 1 Π u -X 1 ∑ + g ), from observations made with the Ultraviolet-Visual Echelle Spectrograph of the European Southern Observatory. We have determined the interstellar column densities and excitation temperatures of C 2 for nine Galactic lines. For seven of these, C 2 has never been observed before, so in this case the still small sample of interstellar clouds (26 lines of sight), where a detailed analysis of C 2 excitation has been made, has increased significantly. This paper is a continuation of previous works where interstellar molecules (C 2 and diffuse interstellar bands) have been analysed. Because the sample of interstellar clouds with C 2 has increased, we can show that the width and shape of the profiles of some diffuse interstellar bands (6196 and 5797 A) apparently depend on the gas kinetic and rotational temperatures of C 2 ; the profiles are broader because of the higher values of the gas kinetic and rotational temperatures of C 2 . There are also diffuse interstellar bands (4964 and 5850 A) for which this effect does not exist.

CHEMICAL ABUNDANCE PATTERNS FOR SHARP-LINED STARS

In order to increase the completeness of the investigations of stellar abundances, we can use spectrum synthesis method, new atomic data and observation of stellar spectra with resolution comparable to solar spectral atlases. We made a brief review of main problems of these three ways. We present new results of abundance determinations in the atmospheres of four stars. The first is the implementation of new atomic data to well known Przybylski`s star. We show that the number of spectral lines, which can be identificated in the spectrum of this star, can be significantly higher. The second example is the investigation of Cyg. We found the abundances of 51 elements in the atmosphere of this mild barium star. The third example is halo star HD221170. Our preliminary abundance pattern consists of 42 elements. The heaviest elements in this pattern are U and Th. The last star is the spectroscopic binary HD153720. The number of elements investigated in the spectra of components of this star is not large, but the results show that the components are Am-stars.

A high-resolution spectral atlas of α persei from 3810 to 8100 Å

We present a high-resolution (λ/δλ = 90,000) spectral atlas of the F5 Ib star α Per covering the 3810-8100 A region. The atlas, based on data obtained with the aid of the echelle spectrograph BOES fed by the 1.8 m telescope at Bohyunsan Observatory (Korea), is the result of the co-addition of a few well-exposed spectra. The final signal-to-noise ratio is ~800 at ~6000 A. The atlas is compared with a synthetic spectrum computed using a code based on Kurucz software and databases. The adopted model atmosphere parameters are Teff = 6240 ± 20 K, log g = 0.58 ± 0.04, and vmicro = 3.20 ± 0.05 km s–1. We also derived an iron abundance of [Fe/H] = -0.28 ± 0.06. The spectral lines of α Per have been identified by matching the synthetic spectrum with the observed one. The atlas is presented in figures and available in digital form on the World Wide Web, along with the synthetic spectrum and spectral line identification tables.

Analysis of optical spectra of V1357 Cyg≡Cyg X-1

Optical spectra and light curves of the massive X-ray binary V1357 Cyg are analyzed. The calculations were based on models of irradiated plane-parallel stellar atmospheres, taking into account reflection of the X-ray radiation, asphericity of the stellar surface, and deviations from LTE for several ions. Comparison of observed spectra obtained in 2004–2005 at the Bohyunsan Observatory (South Korea) revealed variations of the depths of HI lines by up to 18% and of HeI and heavy elements lines by up to 10%. These variations are not related to the orbital motion of the star, and are probably due to variations of the stellar wind intensity. Perturbations of the thermal structure of the atmosphere due to irradiation in various states of Cyg X-1 (including outburst) do not lead to the formation of a hot photosphere with an electron temperature exceeding the effective temperature. As a result, variations of the profiles of optical lines of HI, HeI, and heavy elements due to the orbital motion of the star and variations of the irradiating X-ray flux do not exceed 1% of the residual intensities. Allowing for deviations from LTE enhances the HI and HeI lines by factors of two to three and the MgII lines by a factor of nine, and is therefore required for a fully adequate analysis of the observational data. Analysis of the HI, HeI, and HeII lines profiles yielded the following set of parameters for theOstar at the observing epoch: Teff = 30 500±500 K, log g = 3.31±0.05, [He/H] = 0.42 ± 0.05. The observed HeI line profiles have emission components that are formed in the stellar wind and increase with the line intensity. The abundances of 11 elements in the atmospheres of V1357 Cyg and α Cam, which has a similar spectral type and luminosity class, are derived. The chemical composition of V1357 Cyg is characterized by a strong excess of helium, nitrogen, neon, and silicon, which is related to the binarity of the system.

Variable interstellar lines in spectra of HD 73882

We report a detection of variability in interstellar absorption lines of Cai at 4227 A and Fei at 3860 A in very high signal-to-noise ratio (>1000) UVES and MIKE spectra of HD 73882 (NX Vel) carried out with the aid of 8-m telescope UT2 at Paranal and 6.5-m Magellan Telescope Clay at Las Campanas Observatory, Chile. The spectra, acquired in 2006 January and 2012 January, respectively, clearly show that the intensity and profile shapes of the Cai and Fei lines had dramatically changed within the 6 year period. Other interstellar features, observed along the same line of sight, do not demonstrate strong changes. It is likely that a high velocity CaFe cloud obscured the star between the two observations.

THE LORENTZ FORCE IN ATMOSPHERES OF CP STARS

The slow evolution of global magnetic fields and other dynamical processes in atmospheres of CP magnetic stars lead to the development of induced electric currents in all conductive atmospheric layers. The Lorentz force, which results from the interaction between a magnetic field and the induced currents, may modify the atmospheric structure and provide insight into the formation and evolution of stellar magnetic fields. This modification of the pressure-temperature structure influences the formation of absorption spectral features producing characteristic rotational variability of some spectral lines, especially the Balmer lines (Valyavin et al., 2004 and references therein). In order to study these theoretical predictions we began systematic spectroscopic survey of Balmer line variability in spectra of brightest CP magnetic stars. Here we present the first results of the program. A0p star Aur revealed significant variability of the Balmer profiles during the star`s rotation. Character of this variablity corresponds to that classified by Kroll (1989) as a result of an impact of significant Lorentz force. From the obtained data we estimate that amplitudes of the variation at H, H, H and H profiles reach up to during full rotation cycle of the star. Using computation of our model atmospheres (Valyavin et al., 2004) we interpret these data within the framework of the simplest model of the evolution of global magnetic fields in chemically peculiar stars. Assuming that the field is represented by a dipole, we estimate the characteristic e.m.f. induced by the field decay electric current (and the Lorentz force as the result) on the order of cgs units, which may indicate very fast ( years) evolution rate of the field. This result strongly contradicts the theoretical point of view that global stellar magnetic fields of CP stars are fossil and their the characteristic decay time of about yr. Alternatively, we briefly discuss concurring effects (like the ambipolar diffusion) which may also lead to significant atmospheric currents producing the observable Lorentz force.

Experimental Study of an Advanced Concept of Moderate-resolution Holographic Spectrographs

We present the results of an experimental study of an advanced moderate-resolution spectrograph based on a cascade of narrow-band holographic gratings. The main goal of the project is to achieve a moderately high spectral resolutionwith R up to 5000 simultaneously in the 4300-6800 A visible spectral range on a single standard CCD, together with an increased throughput. The experimental study consisted of (1) resolution and image quality tests performed using the solar spectrum; and (2) a total throughput test performed for a number of wavelengths using a calibrated lab monochromator. The measured spectral resolving power reaches values over R>4000 while the experimental throughput is as high as 55%, which is in good agreement with the modeling results. Comparing the obtained characteristics of the spectrograph under consideration with the best existing spectrographs, we conclude that the used concept can be considered a very competitive and cheap alternative to the existing spectrographs of the given class. We propose several astrophysical applications for the instrument and discuss the prospect of creating its full-scale version.

Unusually high rotational temperature of the CN radical

We analyse a high-resolution, high signal-to-noise spectrogram of the hot reddened star Trumpler 16 112 to find relationships between the physical parameters of the intervening interstellar medium (e.g., the rotational temperature of the CN radical) and the intensities of interstellar lines/bands. We report on the discovery of an interstellar cloud that shows an exceptionally high rotational temperature of CN (4.5 K) and unusually strong Ca I and Fe I interstellar lines. This rare CaFe-type cloud seemingly contains no diffuse band carriers.