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New observations of 53 Persei
De Ridder, J.; Aerts, C.; Gordon, K. D. +1 more
We gathered 37 new spectra of the B star 53 Persei spread over approximately 2 years. On these data, we performed a frequency and a mode analysis. We determined the physical parameters of 53 Persei and placed the star in the theoretical SPB instability strip. We also analysed the 110 photometric observations of the Hipparcos satellite. Our results…
The distance to eight X-ray sources derived from HIPPARCOS observations
Dolan, Joseph F.; Clark, L. Lee
The parallaxes of eight galactic X-ray sources measured by Hipparcos are consistent with zero in all but two cases, 4U1145-619 (= Cen X-5) and HZ43. The parallax and proper motion measured for each of the others, including the Be/neutron star binaries X Per and A0535+26 and the massive X-ray binaries 4U0900-40, 4U1700-37, and Cyg XR-1, are consist…
The evolution from birth to decay of a short-lived active region
Schmieder, Brigitte; Démoulin, Pascal; Mandrini, Cristina H. +3 more
In the following paper we present results of the analysis of NOAA active region 7968, which was the target of a coordinated observing campaign involving the instruments aboard the Solar and Heliospheric Observatory (SOHO), Yohkoh, and ground-based observatories (Bialków, Pic du Midi, and Huairou). This active region was relatively short-lived, and…
Lensed galaxies in Abell 370. II. The ultraviolet properties of arclets and the star formation rate at high redshift
Kneib, J. -P.; Ellis, R. S.; Soucail, G. +1 more
We discuss the statistical properties of faint background galaxies detected in a deep Hubble Space Telescope ultraviolet (F336W) Wide Field Planetary Camera 2 image of the lensing cluster Abell 370 (z=0.37). By combining modelled field galaxy counts at this wavelength with a detailed mass model for the cluster, we develop techniques for predicting…
A comparison of different spectral classification systems for early type stars using HIPPARCOS parallaxes
Paunzen, Ernst
An ``inventory'' of different classification systems were made. Two different surveys for B9 to F2 type stars were chosen in oder to get an unbiased sample of ``normal'' stars. Jaschek & Valbousquet (1997) and Jaschek & Gómez (1998) already investigated the intrinsic consistency of the MK spectral classification systems. But interesting en…
Wavelength shifts of emission line profiles due to velocity fields in the solar corona
Spadaro, D.; Ventura, R.
We have investigated the dependence of the wavelength shift of the coronal emission line profiles on the line of sight velocity of the emitting plasma. The results of our numerical calculations point out that, while the wavelength shift of the collisionally excited component of the line is related to the line of sight velocity by the usual formula…
Identification of lambda Bootis stars using IUE spectra. II. High resolution data
Solano, E.; Paunzen, E.
Stars included in the catalogue of lambda Bootis stars by Paunzen et al. (\cite{Paunzen97}) with high resolution spectra (FWHM: 0.10-0.25 Ä) in the INES Archive of the International Ultraviolet Explorer satellite (IUE) are analyzed here in order to establish membership criteria for the lambda Bootis group. Line-ratios of carbon to heavier elements…
The combination of ground-based astrometric compilation catalogues with the HIPPARCOS Catalogue. I. Single-star mode
Wielen, R.; Dettbarn, C.; Lenhardt, H. +1 more
The combination of ground-based astrometric compilation catalogues, such as the FK5 or the GC, with the results of the ESA Astrometric Satellite HIPPARCOS produces for many thousands of stars proper motions which are significantly more accurate than the proper motions derived from the HIPPARCOS observations alone. In the combination of the basic F…
Chromospheric models for late A-type stars
Catalano, S.; Gouttebroze, P.; Marilli, E. +1 more
The chromospheres of alpha Aql (Altair) and alpha Cep (Alderamin) are investigated. Different semi-empirical model atmospheres are constructed, and the predicted spectra are compared to the observations of the hydrogen Lyman-alpha line (IUE) and carbon (both neutral and ionized) multiplets (GHRS-HST). It is found that chromospheric models at low t…
The H2O abundance and star formation history in rho OPH
Olofsson, Göran; Liseau, René
Iso-Lws observations towards a large number of different positions in the core of the rho Ophc are used to place a limit to the abundance of wide spread H2O. From Nlte excitation and radiative transfer modelling the average line spectrum of the rho Ophc, we find X(H2O) < 10^{-6} to 10^{-5}. We interprete these results with…