Search Publications
Circumstellar matter around M-giants in symbiotic binaries: SY MUSCAE and RW Hydrae
Schmutz, W.; Nussbaumer, H.; Schild, H. +1 more
For the eclipsing symbiotic binary system SY Mus we present evidence for an asymmetric density distribution around the M-giant. We obtain this result from an improved orbital solution. We determine a revised orbital period of P=625.0+/- 0.5 d from UV eclipse observations and a re-analysis of the visual light curve. Based on new radial velocity obs…
Spectroscopic, photometric, and polarimetric study of the Herbig AE candidate HD 36112
Miroshnichenko, A. S.; Savanov, I. S.; Pogodin, M. A. +6 more
We describe observations of the Herbig Ae candidate HD 36112 including high-resolution spectroscopy of photospheric and circumstellar lines, multi-colour photometry and polarimetry. These observations reveal that many features of the observational appearance of HD 36112 are similar to those of `classical' Herbig Ae stars. Among these are: the far …
On the formation of it warm molecular layers
Woitke, P.; Helling, Ch.; Winters, J. M. +1 more
The levitation of the outer atmospheres of AGB stars by pulsations is proposed as possible mechanism to form ``warm molecular layers''. We compare the amounts of CO, H_2O, CO_2 and SO_2 molecules found in an oxygen-rich dynamical model atmosphere with the values derived from recent ISO observations. In the model, the molecules are present in a lay…
New insight into transition region dynamics via SUMER observations and numerical modelling
Doyle, J. G.; Erdélyi, R.; Sarro, L. M. +1 more
We explore the idea that the occurrence of nano-flares in a magnetic loop around the O vi formation temperature could explain the observed red-shift of mid-low transition region lines as well as the blue-shift observed in low coronal lines (T > 6x 105\ K). Observations are compared to numerical simulations of the response of the sola…
ISOCAM observations of the RCrA star formation region
Prusti, T.; Perault, M.; Olofsson, G. +16 more
The results of an ISOCAM survey of the RCrA star formation region are presented. The survey was carried out in two broad-band filters, LW2 (5-8.5 mu m) and LW3 (12-18 mu m). Although it was not possible to map the densest, central region due to saturation problems, 21 sources were identified which showed mid-IR excesses. Most of these sources have…
Lithium abundance and mass
Mallik, Sushma V.
Observations of cool giants have shown that there exists a large range in their lithium abundances even for apparently similar stars. The depletions are large in a majority of them, far in excess of the predictions of the standard stellar evolution models. In order to explore whether the large spread in Li abundances observed in giants can be inte…
Doppler imaging of stellar surface structure. X. The FK Comae-type star HD 199178 = V 1794 Cygni
Strassmeier, K. G.; Lupinek, S.; Dempsey, R. C. +1 more
Doppler imaging is used to derive the surface temperature distribution of the FK Comae star HD 199178 for five observing epochs between 1988 and 1997. Our maps are mainly based on Ca i 6439-Ä line profiles and simultaneous and contemporary BV and VI photometry. All images of HD 199178 are characterized by a large polar spot and several low-latitud…
Transient events in the EUV transition region and chromosphere
Baudin, F.; Keenan, F. P.; Phillips, K. J. H. +2 more
Rapid time cadence observations of the quiet Sun extreme ultraviolet emission, observed by the cds instrument on soho, are discussed. Numerous transient brightenings are observed in network features in both a transition region line (O V 629.73 Ä) and a chromospheric line (He I 584.33 Ä), indicating a dynamic coupling between the chromospheric and …
Discovery of solid HDO in grain mantles
Emerson, J. P.; Teixeira, T. C.; Devlin, J. P. +1 more
The observation of deuterium fractionation in the molecular gas in hot cores is currently interpreted as evaporation of deuterium-rich molecules from the icy grain mantles where they accumulated during the cold, dense cloud core stage. The predicted enrichment in deuterium of the ices has never been observed. This work provides the first detection…
Pulsation models of delta Scuti variables. II. delta Scuti stars as precise distance indicators
Christensen-Dalsgaard, J.; Petersen, J. O.
The Hipparcos period-luminosity relation for high-amplitude delta Scuti stars is discussed as an average period-luminosity-colour-metallicity relation comparing the Hipparcos sample of calibrating stars with a more representative sample taken from McNamara (1997). The Hipparcos relation includes systematic effects of both colour and metallicity an…