Related papers: The peculiar B-type supergiant HD327083
We propose an alternative model for the holographic dark energy in a non-flat universe. This new model differs from the previous one in that the IR length cutoff $L$ is taken to be exactly the event horizon size in a non-flat universe,…
I discuss recent progress in our understanding of exclusive rare and semileptonic decays. I show the impact of HQET when combined with the predictions in the Large Energy Limit of QCD, focusing first on applications to $B\to…
We provide measurements of the Ba isotopic fractions for five metal-poor stars derived with an LTE analysis using 1D model stellar atmospheres. We use high resolution (R\equiv{\lambda}/\Delta{\lambda}=90000-95000), very high signal-to-noise…
Although hydrogen cyanide has become quite a common molecular tracing species for a variety of astrophysical sources, it, however, exhibits dramatic non-LTE behaviour in its hyperfine line structure. Individual hyperfine components can be…
Context. The star HD 87643, exhibiting the "B[e] phenomenon", has one of the most extreme infrared excesses for this object class. It harbours a large amount of both hot and cold dust, and is surrounded by an extended reflection nebula.…
We present an abundance analysis of the low-metallicity benchmark red giant star HD 122563 based on realistic, state-of-the-art, high-resolution, three-dimensional (3D) model stellar atmospheres including non-grey radiative transfer through…
BA-type supergiants show a high potential as versatile indicators for modern astronomy. The focus here is on the determination of accurate and precise atmospheric parameters for a sample of 35 Galactic BA-type supergiants. Some first…
The results of deep long-slit spectroscopy of the extremely low-metallicity blue compact dwarf (BCD) galaxy SBS 0335-052 are presented. Down to intensity levels of 10^{-3 ... -4} of Hbeta, unprecedented for spectroscopy of extra-galactic…
We analysed 337 multi-epoch optical spectra of 38 Herbig Ae/Be (HAeBe) stars to gain insights into the variability behaviour of the circumstellar (CS) atomic gas. Equivalent widths (EWs) and line fluxes of the Halpha, [OI]6300, HeI5876 and…
(abridged) In this work we present the results of an optical and IR study for the curious B[e] star CD-42 11721. This object has a doubtful evolutionary stage, being either a pre-main sequence star (HAeB[e]) or an evolved star (sgB[e]). Our…
In the past, SDSS J160429.12+100002.2 was spectroscopically classified as a blue horizontal branch (BHB) star. Assuming a luminosity that is characteristic of BHB stars, the object's radial velocity and proper motions from Gaia Early Data…
2MASS J20395358+4222505 is an obscured early B supergiant near the massive OB star association Cyg OB2. Despite its bright infrared magnitude (K$_{s}$=5.82) it has remained largely ignored because of its dim optical magnitude (B=16.63,…
We search for LBV stars in galaxies outside the Local Group. Here we present a study of two bright $H\alpha$ sources in the NGC 247 galaxy. Object j004703.27-204708.4 ($M_V=-9.08 \pm 0.15^m$) shows the spectral lines typical for…
We present the change in the Halpha emission-line profile of the spectra of some AeBe Herbig stars. In the spectrum of VY Mon, Halpha may have one of three profile types: P Cyg, P Cyg III or single line in accordance with the brightness…
We report the discovery of a possible close binary system of quasars in SDSS J1048+0055. The [OIII]4959,5007 emission lines are clearly double-peaked, and two discrete radio sources with a projected physical separation of ~20 pc are found…
The blue hypergiant Cyg OB2-12 (B3Ia+) is a representative member of the class of very massive stars in a poorly understood evolutionary stage. We obtained its high-resolution X-ray spectrum using Chandra observatory. PoWR model atmospheres…
HD 50138 is a B[e] star surrounded by a large amount of circumstellar gas and dust. Its spectrum shows characteristics which may indicate either a pre- or a post-main-sequence system. Mapping the kinematics of the gas in the inner few au of…
As potential progenitors of several exotic phenomena including gravitational wave sources, magnetic stars, and Be stars, close massive binary systems probe a crucial area of the parameter space in massive star evolution. Despite the…
Stellar parameters and abundances of Na, Mg, Al, K, Ca, Sr, Ba, and Eu are determined for four very metal-poor stars (-2.66 < [Fe/H] < -2.15) based on non-LTE line formation and analysis of high-resolution (R ~60000 and 90000) high…
Molecular emission has been detected in several Magellanic Cloud B[e] supergiants. In this Letter, we report on the detection of CO band head emission in the B[e] supergiant LHA 115-S 65, and present a K-band near-infrared spectrum obtained…