Search Publications
Towards understanding rapid line-profile and light variations of early-type stars. 3. Some thoughts and reflections
Harmanec, P.
The current situation in the research of rapid line-profile and light variations of early-type stars is critically reviewed. It is suggested that the ultimate understanding of the physical processes causing these variations can only come from an open-minded and complex approach to the problem and from systematic observational effort. It is argued …
Latitudinal properties of the Lyman alpha and O VI profiles in the extended solar corona
Romoli, M.; Poletto, G.; Noci, G. +3 more
We have analysed the latitudinal properties of the profiles of the H I Lyman alpha line at 1215.6 protect Angstroms and of the O VI doublet at 1031.9 protect Angstroms and 1037.6 protect Angstroms in the extended solar corona, between 1.5 R_sun and 2.0 R_sun. Observations have been performed with the UltraViolet Coronagraph Spectrometer (UVCS) on …
Very young massive stars in the Small Magellanic Cloud, revealed by HST
Heydari-Malayeri, M.; Charmandaris, V.; Zinnecker, H. +2 more
High spatial resolution imaging with the Hubble Space Telescope allowed us to resolve the compact H ii region N 81 lying in the Small Magellanic Cloud (SMC). We show the presence of a tight cluster of newborn massive stars embedded in this nebular ``blob'' of ~ 10'' across. This is the first time the stellar content and internal morphology of such…
Isotopic composition of HG and Pt in 5 slowly rotating HgMn stars
Hubrig, S.; Castelli, F.; Mathys, G.
Theoretical models addressing the origin of peculiarities in the spectra of HgMn stars have not been sufficiently constrained so far by the available abundance data. Previous studies of Hg and Pt in samples of HgMn stars often relied on spectra of rather low resolution and low S/N ratio, so that only limited information could be derived from the c…
HST observations of the very young SMC ``blob'' N 88A
Heydari-Malayeri, M.; Charmandaris, V.; Zinnecker, H. +2 more
High-resolution Hubble Space Telescope images have allowed us for the first time to resolve the compact SMC ionized ``blob'' N 88A (diameter ~ ,3''.5 or 1 pc). This very young H ii,region, which is hatching from its natal molecular cloud, is heavily affected by absorbing dust associated with the cloud. The interstellar reddening towards N 88A is o…
EUV and radio observations of an equatorial coronal hole
Kerdraon, A.; Fludra, A.; Landi, E. +1 more
EUV and radio data of an equatorial coronal hole, observed in October 1996 at its central meridian transit, are compared. EUV lines were observed by the CDS instrument onboard SOHO and the radio emission by the Nancay Radioheliograph (France) in the frequency range 164-410 MHz. Using the Differential Emission Measure (DEM), derived from EUV line i…
The dwarf spheroidal galaxy DDO 44: stellar populations and distance
Sarajedini, A.; Dolphin, A. E.; Grebel, E. K. +7 more
We have ground-based and HST WFPC2 imaging of the nearby low surface brightness dwarf spheroidal galaxy DDO 44. For the first time DDO 44 was resolved into stars. The resulting color-magnitude diagram for about 1290 stars show the red giant branch with a tip at I = 23.55+/-0.15, which yields the distance DMW= 3.2+/-0.2 Mpc consistent wi…
Proper motions of faint ROSAT WTT stars in the Chamaeleon region
Terranegra, L.; Lattanzi, M. G.; Spagna, A. +2 more
We present proper motions of 59 stars of the ROSAT All-Sky Survey (RASS) located in direction of the Chamaeleon star forming region (SFR) in the magnitude range B=5.1 - 17 mag. Proper motions of the fainter stars were newly derived utilizing survey Schmidt plates from the GSC II plate archive and from a set of special plates taken with the ESO Sch…
The solar ultraviolet spectrum from 1200 Å to 1560 Å: a radiometric comparison between SUMER/SOHO and SOLSTICE/UARS
Wilhelm, K.; Curdt, W.; Schühle, U. +3 more
After short descriptions of the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrometer onboard SOHO (the Solar and Heliospheric Observatory) and the SOLSTICE (Solar-Stellar Irradiance Comparison Experiment) spectrometer on UARS (the Upper Atmosphere Research Satellite), a radiometric comparison is carried out of solar irradiance …
Evolved, single, slowly rotating ... but magnetically active. The G8-giant HR 1362 = EK Eridani revisited
Strassmeier, K. G.; Henry, G. W.; Hall, D. S. +1 more
We rediscuss the unusual case of the slowly rotating late-type giant HR 1362, which exhibits a very unusual high level of magnetic activity. New BVRI photometry from two robotic telescopes from 1991 through 1998 together with previously published photometric data gives a very precise photometric period of 306.9+/-0.4 days. With the aid of high-res…