Related papers: H alpha emission line profiles of selected post-AG…
Subdwarf B (sdB) stars form the blue end of the horizonal branch. Their peculiar atmospheric abundance patterns are due to diffusion processes. However, diffusion models fail to explain these anomalies quantitatively. From a NLTE model…
We present echelle long-slit optical spectra of a sample of objects evolving off the AGB, most of them in the pre-planetary nebula (pPN) phase, obtained with the ESI and MIKE spectrographs at Keck-II and Magellan-I, respectively. The total…
Aims: To model broad H-alpha wings observed in symbiotic binaries by an optically thin, bipolar stellar wind from their hot components as an alternative to that considering the Raman scattering of Ly-beta photons on atomic hydrogen.…
This paper describes observations of a new phenomenon in evolved mass-losing AGB stars: the presence of two winds with different expansion velocities. CO(2-1) and CO(3-2) line emission was observed for 45 AGB stars at high velocity…
High signal-to-noise, representative spectra of star-forming galaxies at z~2, obtained via stacking, reveal a high-velocity component underneath the narrow H-alpha and [NII] emission lines. When modeled as a single Gaussian, this broad…
We present new Hubble Space Telescope Cosmic Origins Spectrograph far-ultraviolet (far-UV) spectroscopy and Keck Echellete optical spectroscopy of 11 ultraluminous infrared galaxies (ULIRGs), a rare population of local galaxies experiencing…
The slow, dense winds observed in evolved asymptotic giant branch (AGB) stars are usually attributed to a combination of dust formation in the dynamical inner atmosphere and momentum transfer from stellar photons interacting with the newly…
This paper explores the effects of post-AGB winds driven solely by magnetic pressure from the stellar surface. It is found that winds can reach high speeds under this assumption, and lead to the formation of highly collimated…
We have detected the (0,11c,0)J=3-2 and (0,0,0)J=8-7 transitions of HCN towards the S star {chi} Cygni. The excitation requirements of these transitions are too high to be satisfied in the outer envelope of the star, and the emission must…
We present spectra of a large sample of low-metallicity blue compact dwarf galaxies which exhibit broad components in their strong emission lines, mainly in Hbeta, [O III]4959, 5007 and Halpha. Twenty-three spectra have been obtained with…
A new type of peculiarity -- a splitting or asymmetry of strong absorption lines, is found in the optical spectra of selected post-AGB stars with C-rich circumstellar envelopes. The effect is maximal in BaII lines whose profile is split…
From an analysis of the spectrum (4000\AA to 8800\AA) of HD~101584 it is found that most of the neutral and single ionized metallic lines are in emission. The forbidden emission lines of [OI] 6300\AA and 6363\AA and [CI] 8727\AA are…
Spectral analyses of H-deficient post-AGB stars have shown that a small group of four extremely hot objects exists which have almost pure He absorption-line spectra in the optical. These are classified as O(He) stars. For their evolution…
We report optical and near-infrared spectra of the central star of the radio source G79.29+0.46, a candidate luminous blue variable. The spectra contain numerous narrow (FWHM < 100 km/s emission lines of which the low-lying hydrogen lines…
Context. In 1985, at the end of the active phase 1977-1986, a broad (4000 km/s) Ly alpha line appeared in the symbiotic system CH Cygni that had never been observed previously. Aims. In this work we investigate the origin of this anomalous…
The late stellar evolutionary phases of low and intermediate-mass stars are strongly constrained by their mass-loss rates. The wind surrounding cool evolved stars frequently shows non-spherical features, thought to be due to an unseen…
Spectroscopic data in wavelengths 900--3000A have been obtained in a low flux state of the nucleus of the Seyfert 1 galaxy NGC 3516. The line profiles show P Cygni characteristics, particularly in O VI 1032A, and are compared with data from…
We propose an explanation to the puzzling appearance of a wide blue absorption wing in the He I 10830A P-Cygni profile of the massive binary star Eta Carinae several months before periastron passage. Our basic assumption is that the…
We present a catalogue including 11,204 spectra for 10,436 early-type emission-line stars from LAMOST DR2, among which 9,752 early-type emission-line spectra are newly discovered. For these early-type emission-line stars, we discuss the…
CO(J = 2-1) and SiO(J = 5-4) emission has been observed from the molecular envelope around the nearby S star pi Gru. The CO line profile differs from the usual parabolic shape seen in uniformly expanding envelopes; it has a Voigt-like…