Y. Beletsky

HYDROXYL CATION IN TRANSLUCENT INTERSTELLAR CLOUDS

High-quality spectra acquired at the European Southern Observatory enabled us to discover a very weak spectral feature of the OH+ molecule, near 3584 A. The species likely shares environments with another molecular ion, CH+. Its abundance is by a factor of 30 lower than that of neutral OH.

The relation between column densities of interstellar OH and CH molecules

We present a new, close relation between column densities of OH and CH molecules based on 16 translucent sightlines (six of them new) and confirm the theoretical oscillator strengths of the OH A-X transitions at 3078 and 3082 A (0.001 05, 0.000 648) and CH B-X transitions at 3886 and 3890 A (0.003 20, 0.002 10), respectively. We also report no difference between observed and previously modelled abundances of the OH molecule.

The relation between interstellar OH and other simple molecules

We discuss the close relation between the column densities of interstellar OH and CH molecules. Our results are obtained on the basis of 10 new sightlines. The OH molecule seems not to be spatially correlated with either CH + or CN simple species.

Observational test of the CH cation oscillator strengths

We revise measurements of the positions and oscillator strengths using spectral features in the CH + A - X system, and by using high-resolution, echelle spectra of 36 stars and assuming that its wavelength and oscillator strength as given in the literature for the (0,0) transition, i.e. 4232.548 A and 0.00545 respectively, are correct. The recommended oscillator strengths of the lines at 3957.689, 3745.308, 3579.024, and 3447.077 A are found to be (in units of 10 -5 ) 342, 172, 75, and 40, respectively. The estimated column densities of the CH cation toward the observed targets are also presented.

New Galactic Candidate Luminous Blue Variables and Wolf-Rayet Stars

We have undertaken a near-infrared spectral survey of stars associated with compact mid-IR shells recently revealed by the MIPSGAL (24 micron) and GLIMPSE (8 micron) Spitzer surveys, whose morphologies are typical of circumstellar shells produced by massive evolved stars. Through spectral similarity with known Luminous Blue Variable (LBV) and Wolf-Rayet (WR) stars, a large population of candidate LBVs (cLBVs) and a smaller number of new WR stars are being discovered. This significantly increases the Galactic cLBV population and confirms that nebulae are inherent to most (if not all) objects of this class. Keywords - stars: emission-line, Be, stars: mass loss, stars: winds, outflows, stars: Wolf-Rayet

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.

Mapping Extragalactic Molecular Clouds: Centaurus a (NGC 5128)

We propose a novel albeit proven technique that uses dust extinction as a tracer of H2 to study the physical structure of a large sample of extragalactic GMCs. We present results for the nearby galaxy NGC 5128 where we were able to construct an extinction map at subarcsec resolution (≈10 pc)