相关论文: Near-infrared characterization of four massive sta…
The upper region of the Hertzsprung-Russell diagram is populated by massive stars in a diversity of evolutionary stages, and the classification of these stars is often based on observed characteristics exclusively in the optical spectral…
We present HR Diagrams for the massive star populations in M31 and M33 including several different types of emission-line stars: the confirmed Luminous Blue Variables (LBVs), candidate LBVs, B[e] supergiants and the warm hypergiants. We…
The advanced stages of several high-mass stars are characterized by episodic mass loss shed during phases of instability. Key for assigning these stars a proper evolutionary state is to assess the composition and geometry of their ejecta…
An increasing number of non-terminal eruptions are being found in the numerous surveys for optical transients. Very little is known about these giant eruptions, their progenitors and their evolutionary state. A greatly improved census of…
In this series of papers we have presented the results of a spectroscopic survey of luminous and variable stars in the nearby spirals M31 and M33. In this paper, we present spectroscopy of 132 additional luminous stars, variables, and…
We discuss moderate resolution spectra, multicolor photometry, and light curves of thirty-one of the most luminous stars and variables in the giant spiral M101. The majority are intermediate A to F-type supergiants. We present new…
The role of episodic mass loss in massive star evolution is one of the most important open questions of current stellar evolution theory. Episodic mass loss produces dust and therefore causes evolved massive stars to be very luminous in the…
Massive evolved stars in transition phases, such as Luminous Blue Variables (LBVs), B[e] Supergiants (B[e]SGs), and Yellow Hypergiants (YHGs), are not well understood, and yet crucial steps in determining accurate stellar and galactic…
This study presents an investigation of nearly two dozen candidate Luminous Blue Variables (cLBVs) in the galaxies M31 and M33. Eight stars have been studied in detail, while an additional sixteen objects are briefly mentioned. Multi-epoch…
Luminous blue variables (LBVs) are expected to play an important role in massive stellar evolution as well as being the progenitors of some of the most luminous supernovae known. In this paper we provide a multiwavelength study of the…
New multi-epoch, mid-infrared (8-13 microns) spectrophotometric observations are presented for 30~late-type stars. The observations were collected over a four year period (1994-1997), permitting an investigation of the mid-infrared spectral…
We present ESO/VLT spectra in the 2.9--4.1 micron range for a large sample of infrared stars in the Large Magellanic Cloud (LMC), selected on the basis of MSX and 2MASS colours to be extremely dust-enshrouded AGB star candidates. Out of 30…
Luminous Blue Variable (LBV) stars are evolved massive objects, previous to core-collapse supernova. LBVs are characterized by photometric and spectroscopic variability, produced by strong and dense winds, mass-loss events and very intense…
Increasing the statistics of spectroscopically confirmed evolved massive stars in the Local Group enables the investigation of the mass loss phenomena that occur in these stars in the late stages of their evolution. We aim to complete the…
Mass-loss from evolved stars chemically enriches the ISM. Stellar winds from massive stars and their explosions as SNs shape the ISM and trigger star formation. Studying evolved stars is fundamental for understanding galaxy formation and…
We investigate the molecular and dusty environment of OH/IR stars in order to characterize the mass-loss process during the tip-AGB superwind phase. Employing the AMBER instrument at the VLT Interferometer we obtained near-infrared H- and…
Recent ground-based mid-infrared spectra of 29 late-type stars, most with substantial dust shells, are compared to ground-based spectra of these stars from the 1960s and 1970s and to IRAS-LRS spectra obtained in 1983. The spectra of about…
The progenitors of Type IIP supernovae have an apparent upper limit to their initial masses of about 20 solar masses, suggesting that the most massive red supergiants evolve to warmer temperatures before their terminal explosion. But very…
An increasing number of non-terminal giant eruptions are being observed by modern supernova and transient surveys. But very little is known about the origin of these giant eruptions and their progenitors, many of which are presumably very…
We report spectra obtained with the Spitzer Space Telescope in the wavelength range between 14 microns and 35 microns of 19 nearby main-sequence stars with infrared excesses. The six stars with strong dust emission show no recognizable…