G. A. Galazutdinov

The Rotational Excitation Temperature of the λ6614 Diffuse Interstellar Band Carrier

Analysis of high spectral resolution observations of the λ6614 diffuse interstellar band (DIB) line profile shows systematic variations in the positions of the peaks in the substructure of the profile. These variations—shown here for the first time—can be understood most naturally in the framework of rotational contours of large molecules, where the variations are caused by changes in the rotational excitation temperature. We show that the rotational excitation temperature for the DIB carrier is likely significantly lower than the gas kinetic temperature—indicating that for this particular DIB carrier angular momentum buildup is not very efficient.

Diffuse Interstellar Bands: Physical Conditions That Facilitate the Formation or Preservation of Their Carriers

This paper suggests that the formation and/or preservation of the carriers of at least some of the diffuse interstellar bands (DIBs) depends on the level of ionization of certain interstellar atoms, such as potassium and calcium inside H I clouds. The spectral lines of these elements are apparently well correlated with the narrow diffuse bands, such as 5797 or 6379 A. Thus, the physical conditions that facilitate the growing abundance of neutral alkali atoms also facilitate the formation or preservation of the carriers of the narrow diffuse bands. The broad features, such as 5780 or 6284 A, apparently originate in different ionization conditions.

Circumstellar Disk around HD 143275 and Interstellar Absorption

This paper presents a collection of spectra of the star HD 143275 (δ Sco), acquired during the last 11 years. During this period, stellar absorption lines turned into emission features possibly originating in the circumstellar disk. We demonstrate that the circumstellar shell does not produce any components of interstellar absorption features (atomic lines, molecular features, and diffuse interstellar bands), which remain of the same equivalent widths during the whole period covered by our observations.

A detailed spectroscopy of the carbon-rich star BD +57° 2161

An LTE abundance analysis based on high-resolution spectra is presented for the carbon-rich star BD +57° 2161, whose evolutionary status is unknown. With [C/Fe] = +0.4 dex and a mean s-process overabundance of [s/Fe] ≃ +1.5 dex the peculiar atmospheric composition of BD +57° 2161 is confirmed. The 12 C/ 13 C abundance ratio was found to be about 10. The mild iron deficiency, [Fe/H] = -0.2, supports the idea that BD +57° 2161 could be an old-disk-population object. Radial-velocity measurements confirm the binary nature of the star. Therefore the peculiar chemical composition could be due to the mass transfer from the secondary - AGB star in the past. Orbital parameters are estimated for another star of this group, BD +75° 348.

The spectral variations of the O-type runaway supergiant HD 188209

We report spectral time series of the late O-type runaway supergiant HD 188209. Radial velocity variations of photospheric absorption lines with a possible quasi-period ~ 6.4 days have been detected in high-resolution echelle spectra. Night-to-night variations in the position and strength of the central emission reversal of the Ha profile occuring over ill-defined time-scales have been observed. The fundamental parameters of the star have been derived using state-of-the-art plane--parallel and unified non-LTE model atmospheres, these last including the mass-loss rate. The derived helium abundance is moderately enhanced with respect to solar, and the stellar masses are lower than those predicted by the evolutionary models. The binary nature of this star is not suggested either from Hipparcos photometry or from radial velocity curves.

A search for fine structure inside high resolution profiles of weak diffuse interstellar bands

This paper presents a survey of the high-resolution profiles of selected, moderately weak diffuse interstellar bands (DIBs) between 4725 and 6730 A. In very high signal-to-noise spectra, obtained as a result of averaging several individual exposures of reddened, early-type stars that show Doppler splitting of < 2k m s −1 in interstellar gas lines, the profiles seem to have a substructure. This supports the molecular origin hypothesis for DIBs. We studied the profiles of the diffuse interstellar bands at wavelengths of 4726.33, 4963.85, 5418.89, 5541.74, 5544.95, 5546.46, 5762.73, 5766.05, 5769.09, 6439.41, 6445.53, 6449.16, 6729.28 A.