Search Publications
A sample of planetary nebulae observed by HIPPARCOS
Pottasch, S. R.; Jasniewicz, G.; Acker, A. +1 more
By using HIPPARCOS data (magnitudes, parallaxes, proper motions), (1) we determine new values of the apparent luminosity of the central stars of 19 planetary nebulae, (2) we discuss their distance and position on the T/L diagram. By comparison with the distances determined by individual or statistical methods, we see that most of these ``ground" d…
Oscillations of sunspot magnetic fields
Solanki, S. K.; Scherrer, P. H.; Stenflo, J. O. +2 more
We report on velocity and magnetic field oscillations observed in sunspots using the MDI instrument onboard SOHO. In addition to the well-known velocity oscillations, the data clearly show highly localised oscillations of the magnetogram signal in different parts of the sunspots. We show that only oscillations of the magnetic field vector can prod…
ISO-SWS spectra of the C-rich AGB star R Scl and dynamical model atmospheres
Hron, J.; Kerschbaum, F.; Aringer, B. +3 more
We have monitored the spectral variations of the carbon rich AGB star R Scl in the 2-45 mu m range using the ISO-SWS instrument. We have also computed hydrostatic and hydrodynamic model atmospheres and corresponding synthetic spectra representative for two phases of R Scl. There is good qualitative agreement between observations and models in the …
Far-infrared emission of intracluster dust in the Coma galaxy cluster
Lemke, D.; Haas, M.; Mattila, K. +2 more
The ISOPHOT C200 camera aboard ISO has been used to observe the extended far infrared (FIR) emission from the Coma cluster of galaxies. Two scans with 48arcmin length across the cluster, each at 120 microns and 185 microns , were obtained at crossing position angles. The profiles of the surface brightness ratio I_120 microns / I_185 microns along …
Mass determination of astrometric binaries with Hipparcos. II. Selection of candidates and results
Mignard, F.; Martin, C.
In a previous paper (\cite{Mar97}) we have shown that for double stars with orbital periods smaller than about 25 years, it was possible to determine from the Hipparcos data, the mass ratio B of the components or the difference between the mass and intensity ratios, beta -B, provided the orbital elements of the relative orbit are available. From a…
The evolutionary status of activity-selected solar-type stars and of T Tauri stars as derived from HIPPARCOS parallaxes: evidence for long-lived T Tauri disks?
D'Antona, F.; Micela, G.; Favata, F. +1 more
We have used the Hipparcos parallaxes to study the evolutionary status of a sample of stars with spectral types from late F to M0 (hereafter ``solar-type stars''), selected on the basis of their activity, mainly from Einstein-based surveys. The parallaxes have been used to place the objects in the H-R diagram, determining their age by comparison w…
The ISOPHOT far-infrared serendipity north ecliptic pole minisurvey
Kessler, M. F.; Burgdorf, M.; Lemke, D. +11 more
The ISOPHOT Serendipity Survey fills the otherwise unused slew time between ISO's fine pointings with measurements in an unexplored wavelength regime near 200 microns. In order to test point source extraction software, the completeness of the detected objects as well as the astrophysical content we investigate a 100 sq degr field near the North ec…
Photospheric metals in hot DA white dwarfs
Dreizler, S.; Wolff, B.; Koester, D. +1 more
Previous observations of the soft X-ray and EUV region with the Einstein, EXOSAT, and ROSAT satellites have indicated the presence of photospheric absorbers in most DA white dwarfs with {T_eff} ga 40000K. Several of these objects have now been observed with the Extreme Ultraviolet Explorer (EUVE). Since the detection of individual metal lines is r…
Molecular gas phase counterparts to solid state grain mantles features: implication for gas/grain chemistry
Boulanger, F.; Puget, J. -L.; Dartois, E. +4 more
We present ISO SWS (AOT6) observations of the protostellar object RAFGL 7009S. This source is particularly interesting for the characterisation of chemistry arising from grain surfaces and mantles, since the solid state features of many simple molecules such as H_2O, CO, CO_2, (13) CO_2 and CH_4 are detected, together with weaker features not yet …
The comptonized X-ray source X 1724-308 in the globular cluster Terzan 2
Stella, L.; Parmar, A. N.; Guainazzi, M. +3 more
We report on the BeppoSAX observation of the X-ray source X 1724-308 in the globular cluster Terzan 2. The broadband spectrum can be described as the superposition of a power-law with photon spectral index Gamma =~ 1.6-1.9 and a thermal component with typical temperature kT ~ 1 keV. X 1724-308 is detected in the PDS up to 150 keV with a S/N ratio …