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WN stars in the LMC: Parameters and atmospheric abundances
Hamann, W. -R.; Koesterke, L.
The spectra of 18 WN stars in the Large Magellanic Cloud (LMC) are quantitatively analyzed by means of "standard" Wolf-Rayet model atmospheres, using the helium and nitrogen lines as well as the spectral energy distribution. The hydrogen abundance is also determined. Carbon is included for a subset of 4 stars. The studied sample covers all spectra…
VLT-detection of two edge-on Circumstellar Disks in the rho Oph dark cloud
Motohara, K.; Iwamuro, F.; Brandner, W. +7 more
Observations of the rho Ophiuchi star forming region with VLT ANTU and ISAAC under 0\farcs35 seeing conditions reveal two bipolar reflection nebulosities intersected by central dust lanes. The sources (OphE-MM3 and CRBR 2422.8-3423) can be identified as spatially resolved circumstellar disks viewed close to edge-on, similar to edge-on disk sources…
Comparison between observed and theoretical Red Giant Branch luminosity functions of galactic globular clusters
Zoccali, M.; Piotto, G.
V-band luminosity functions (LF) have been obtained for the upper main-sequence (MS), sub-giant branch (SGB) and red giant branch (RGB) of 18 galactic globular clusters (GGC) from HST data. A comparison with four sets of theoretical models has been performed. In contrast with what was found in several previous works, a good general agreement has b…
Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases
Sciortino, S.; Maggio, A.; Pizzolato, N.
We have investigated the variation of coronal X-ray emission during early post-main-sequence phases for a sample of 120 late-type stars within 100 pc, and with estimated masses in the range 1-3 Msun, based on Hipparcos parallaxes and recent evolutionary models. These stars were observed with the ROSAT/PSPC, and the data processed with t…
Rapidly oscillating Ap stars versus non-oscillating Ap stars
Hubrig, S.; North, P.; Mathys, G. +1 more
The positions in the HR diagram and the kinematic characteristics of rapidly oscillating and non-oscillating chemically peculiar stars are obtained using new Hipparcos proper motions and parallaxes, and our own radial velocity measurements. We find that rapidly oscillating stars, as a group, are (-0.47 +/- 0.34) mag above the zero-age main sequenc…
The Galactic disk: study of four low latitude Galactic fields
Vallenari, A.; Schmidtobreick, L.; Bertelli, G.
We present deep V and I photometry of stellar fields in four previously unstudied low latitude regions of the Galactic disk. All observed fields are located at the western side of the Galactic Center in the direction of the Coalsack-Carina region. They are chosen on the large scale surface photometry of the Milky Way (Hoffmann et al., 1998 and Kim…
Element abundances in cool white dwarfs. I. The DZA white dwarfs L 745-46A and Ross 640
Wolff, B.; Koester, D.
The standard explanation for the presence of photospheric metals in white dwarfs of spectral type DZ and related types is a combination of episodic accretion from the interstellar medium and diffusion of heavy elements downwards in the atmosphere on time scales of typically 106 years. Much of the empirical data on atmospheric parameters…
ISO SWS-LWS observations of the prototypical reflection nebula NGC 7023
Cernicharo, J.; Gerin, M.; Fuente, A. +2 more
We present SWS and LWS ISO observations towards a strip across the photodissociation region (PDR) in the reflection nebula NGC 7023. SWS02 and LWS01 spectra have been taken towards the star and the brightest infrared filaments located NW and SW from the star (hereafter NW and SW PDRs). In addition, SWS02 spectra have been taken towards two interme…
Ultraviolet fluorescence lines of Fe II observed in satellite spectra of the symbiotic star RR Telescopii
Johansson, S.; Hartman, H.
By examining all emission lines of Fe II in high resolution satellite spectra of the symbiotic star RR Tel we have made a systematic study of fluorescence lines in the ultraviolet wavelength region 1200-3000 Ä. We list 33 energy levels of Fe II that are selectively excited in the stellar system by photons from strong lines of H, He II, Si III, O I…
Ca II activity and rotation in F-K evolved stars
Pasquini, L.; de Medeiros, J. R.; Girardi, L.
Ca II H and K high resolution observations for 60 evolved stars in the field and in 5 open clusters are presented. From these spectra chromospheric fluxes are derived, and a homogeneous sample of more than 100 giants is built adding data from the literature. In addition, for most stars, rotational velocities were derived from CORAVEL observations.…