Search Publications
A spectral analysis of the hydrogen-deficient star HD 144941.
Jeffery, C. S.; Harrison, P. M.
HD144941 is a B type hydrogen-deficient star. Previous analysis has suggested that its effective temperature and surface gravity are similar to the nitrogen rich H-deficient star V652 Her. However, its H/He ratio puts it between the classifications of an extreme and an intermediate helium star, and its low C and N abundances make it unique amongst…
Spectropolarimetry and nebular geometry of the symbiotic star HBV 475.
Schild, H.; Schmid, H. M.
We present and discuss spectropolarimetry of the Raman scattered emission features at λ6825 and λ7082 of the symbiotic nova HBV 475. Meaningful interpretation in relation to the orbital phase requires an improved ephemeris and we first review available photometry and deduce a new period of 956.5d and minimum epoch at JD 2444890. The flux of the λ6…
Injection of large grains into orbits around comet nuclei.
Fulle, M.
Starting from the nucleus surface, the motion of dust boulders of diameters larger than the solar radiation pressure resonance size (Richter & Keller, 1995Icar..114..355R) is investigated by numerical integration of the motion equation for times larger than the comet orbital period. The motion equation takes into account the comet nucleus grav…
Nitrogen V in the wind of the pre-main sequence Herbig AE star AB Aurigae
Bouret, J. -C.; Catala, C.; Simon, T.
Recent GHRS observations of the Herbig Ae star AB Aur demonstrate the presence of N V in the wind of this star. This result reveals temperatures much higher than those previously considered for the wind of AB Aur. We show that homogeneous spherically symmetric models are unable to reproduce the available observations, including the C IV resonance …
Search for brightness fluctuations in the zodiacal light at 25 MU M with ISO
Abraham, Peter; Lemke, Dietrich; Leinert, Christoph
We mapped at 25 mu m five ~0.5(deg) x0.5(deg) fields at low, intermediate and high ecliptic latitude with the photometer onboard the Infrared Space Observatory. The goal was to search for potential structures in the zodiacal light. No structures were seen in these five sample fields. For an aperture of 3' diameter we find an upper limit for the un…
Local interstellar cloud electron density from magnesium and sodium ionization: a comparison.
Ferlet, R.; Lallement, R.
The ambient interstellar plasma density (i.e. the plasma density of the interstellar medium surrounding the Sun) directly governs the structure and the size of our heliosphere. Information on this density can be derived from the ionization states of the interstellar species which can be detected in absorption along the paths to the nearby stars, a…
Principles of statistical astrometry
Wielen, R.
We present a coherent scheme of `statistical astrometry' for high-precision measurements. Statistical astrometry provides methods and tools for treating quantitatively the overall statistical effect of the presence of many individually unresolved or unmodelled astrometric binaries in a stellar ensemble. The non-linear motions of the photo-centers …
On the evolutionary status of λ Bootis stars using HIPPARCOS data.
Paunzen, E.
We have used the Hipparcos data to derive absolute magnitudes and thus the evolutionary status for the group of λ Bootis stars. The origin for this small group of nonmagnetic, chemically peculiar stars, still remains a matter of debate. Using new evolutionary tracks, we are able to provide an age determination to distinguish between the two propos…
HST-GHRS observations of candidate β Pictoris-like circumstellar gaseous disks.
Deleuil, M.; Ferlet, R.; Vidal-Madjar, A. +6 more
We present HST-GHRS observations of four stars in search of β Pictoris-like circumstellar gaseous disks. We detected gas around HR 10, HR 2174 and 51 Oph at large distances from the stars; this gas is circumstellar since the absorption lines from very excited levels require densities incompatible with those found in the diffuse interstellar medium…
A multiwavelength study of LS II+34 26: a hot post-AGB star in the process of becoming a planetary nebula.
Pottasch, S. R.; de Martino, D.; Parthasarathy, M. +4 more
We present the results from a multiwavelength analysis of LS II+34 26, recently identified as a low mass post-AGB star and not a massive population I B-type star, as previously thought. We confirm that the central star is a carbon-poor post-AGB star surrounded by a very low excitation and compact nebula. Spectroscopic monitoring carried out since …