Related papers: Dust and Gas around lambda Bootis Stars
AGB stars are one of the main sources of dust production in the Galaxy. However, it is not clear what this process looks like and where the dust is condensing in the circumstellar environment. By characterizing the location of the dust and…
Debris disks are considered to be gas-poor, but recent observations revealed molecular or atomic gas in several 10-40 Myr old systems. We used the APEX and IRAM 30m radiotelescopes to search for CO gas in 20 bright debris disks. In one…
Emission-line stars are typically surrounded by dense circumstellar material, often in form of rings or disc-like structures. Line emission from forbidden transitions trace a diversity of density and temperature regimes. Of particular…
Discs of dusty debris around main-sequence star indicate fragmentation of orbiting planetesimals, and for a few A-type stars, a gas component is also seen that may come from collisionally-released volatiles. Here we find the sixth example…
Long-duration gamma-ray bursts are associated with the explosions of massive stars and are accordingly expected to reside in star-forming regions with molecular gas (the fuel for star formation). Previous searches for carbon monoxide (CO),…
In the interstellar medium of the Milky Way, certain elements -- e.g., Mg, Si, Al, Ca, Ti, Fe -- reside predominantly in interstellar dust grains. These grains absorb, scatter, and emit electromagnetic radiation, heat the interstellar…
Major improvements in models of chemically peculiar stars have been achieved in the past few years. With these new models it has been possible to test quantitatively some of the processes involved in the formation of abundance anomalies and…
Synthetic spectra of Arcturus computed with the latest theoretical stellar atmospheres disagree strongly with both the spectral energy distribution and with the spectroscopic data for $\lambda < 4000$ \AA , even though the stellar…
Disk warps around classical T Tauri stars (CTTS) can periodically obscure the central star for some viewing geometries. For these so-called AA Tau-like variables, the obscuring material is located in the inner disk and absorption…
In this contribution, we revisit the model of a dust-enshrouded star orbiting a low-luminosity galactic nucleus (Zaja\v{c}ek et al. 2014, 2016, 2017). Although it is quite challenging for dust to survive in hot X-ray-emitting plasma…
FS CMa type stars are a recently described group of objects with the B[e] phenomenon that exhibit strong emission-line spectra and strong IR excesses. In this paper we report the first attempt for a detailed modeling of IRAS 00470+6429, for…
High resolution (lambda / Delta-lambda = 50,000) K-band spectra of massive, embedded, young stellar objects are presented. The present sample consists of four massive young stars located in nascent clusters powering Galactic giant H II…
White dwarf stars frequently experience external pollution by heavy elements, and yet the intrinsically carbon-enriched DQ spectral class members fail to exhibit this phenomenon, representing a decades-old conundrum. This study reports a…
We investigate the star formation and dust extinction properties of very luminous infrared galaxies whose spectra display a strong Hdelta line in absorption and a moderate [OII] emission (e[a] spectrum). This spectral combination has been…
We present millimeter imaging observations in the 1200 micron continuum of the disk around beta Pictoris. With the 25 arcsec beam, the beta Pic disk is unresolved perpendicularly to the disk plane (< 10 arcsec), but slightly resolved in the…
We report the results of a search for gas phase atomic metals in the circumstellar envelope of the AGB carbon star IRC+10216. The search was made using high resolution (R=50000) optical absorption spectroscopy of a backgound star that…
B[e] Supergiants are a phase in the evolution of some massive stars for which we have observational evidence but no predictions by any stellar evolution model. The mass-loss during this phase creates a complex circumstellar environment with…
We are investigating the circumstellar material for a sample of B[e] stars using high spectral resolution data taken in the optical and near-infrared regions with ESO/FEROS and ESO/CRIRES spectrographs, respectively. B[e] stars are…
eta Telescopii is a ~23 Myr old A-type star surrounded by an edge-on debris disc hypothesised to harbour gas. Recent analysis of far- and near-ultraviolet spectroscopic observations of eta Tel found absorption features at ~-23 km/s and ~-18…
Over the past fifteen years, surveys mainly at millimeter wavelengths have led to the discovery of $\sim$20 gas-bearing debris disks, most of them surrounding young intermediate-mass stars. Exploring the properties and origin of this gas…