Search Publications
HIPPARCOS great-circle reduction - Theory, results and intercomparisons
van der Marel, Hans; Petersen, Carsten
In this paper some of the results of the great-circle reduction in the two data reduction consortia (NDAC and FAST) are presented. It is shown that the root-mean-square (rms) error of the great-circle abscissa of stars brighter than 10 mag is between 3-5 milli-arcsec. This is as was expected before launch, even in spite of the fact that the data-s…
A study of the optical and ultraviolet spectral characteristics and the circumstellar material around the new luminous blue variable WRA 751.
Perez, M. R.; The, P. S.; de Winter, D. +1 more
The LBV characteristics of the new LBV candidate WRA 751 suggested by Hu et al. (1990) are studied in greater detail. A comparison is made with observational characteristics of the well-known LBVs Ag Car and HR Car using photometric and spectroscopic data of Hu et al. supplemented with an IUE spectrum and direct CCD images in H-alpha, blue, and re…
The active phase of the symbiotic star BF Cygni.
Gonzalez-Riestra, R.; Cassatella, A.; Fernandez-Castro, T. +1 more
The activity phase of BF Cygni discovered in May 1989 and which lasted about two years is examined. The UV emission lines, usually strong during quiescence, were not detectable during the outburst. UV high-resolution spectra in the outburst indicate the development of an expanding shell giving rise to a considerable number of violet-shifted absorp…
Mg II absolute line profiles for late-type stars and for spatially-resolved solar regions.
Pallavicini, R.; Cerruti-Sola, M.; Cheng, C. -C.
The authors present the results of a comparison of Mg II h and k line profiles and fluxes for late-type stars observed with IUE and for spatially resolved solar regions observed at comparable resolution by the NRL Spectrograph on Skylab. They show that the spatially resolved solar observations are in good agreement with the disk integrated stellar…
High-precision VLBI astrometry of the radio-emitting star sigma rho a step in linking the HIPPARCOS and extragalactic reference frames.
Preston, Robert A.; Lestrade, Jean-Francois; Phillips, Robert B. +1 more
VLBI observations of the optically bright radio-emitting star Sigma Coronae Borealis (Sigma CrB) have yielded its position relative to an angularly nearby quasar, its annual proper motion and its trigonometric parallax with formal uncertainties slightly better than 0.2 milliarcsec. This is the first result of the VLBI astrometric program we are co…
Photometric calibration of the International Ultraviolet Explorer (IUE) at low resolution: the LWP camera.
Gonzalez-Riestra, R.; Lloyd, C.; Cassatella, A. +2 more
The authors present and discuss the low resolution absolute calibration for the LWP camera of the International Ultraviolet Explorer (IUE). The calibration, implemented in routine processing of LWP low resolution images on December 22, 1987 at both GSFC and VILSPA IUE ground stations, is based on the last set of Intensity Transfer Function (ITF2) …
Global block adjustment simulations using the CPC 2 data structure
Zacharias, N.
Over 276,000 star positions on 5695 plates covering the entire southern hemisphere with a four-fold overlap pattern are used in rigorous block adjustment (BA) simulations to estimate the positional accuracy in terms of random and zonal systematic errors. A significant improvement of such global BA solutions are found as compared to BA solutions of…
IUE observations of UB-bright stars in M 3.
Cacciari, C.; Buonanno, R.; Corsi, C. E. +2 more
IUE UV observations of three "UV-bright" stars in M3 are presented. The brightest object - vZ1128 - is confirmed to be a bright Post-AGB star with logL/Lsun=3.09 and Te=30,000 K, which contributes about 25% of the integrated UV light from the cluster at λ=1500Å. The nature of the two other stars, i.e. 524 (logL/Lsun
A photometric survey of the eclipsing RS CVn-type system RZ Eridani : starspot variability, circumstellar matter, tidal evolution.
North, P.; Burki, G.; Kviz, Z.
Results are presented of monitoring of the RS CVn-type eclipsing binary RZ Eridani, observed in the seven colors of the Geneva photometric system between November 1977 and April 1989. It is shown that the primary is an A8-F0IV star, which was stable during the 12 years of the survey. The secondary component, a G8-K0IV-III star, exhibits three kind…
The X-ray variability of the Seyfert galaxy NGC 6814.
Fiore, F.; Massaro, E.; Barone, P.
We present the results of an accurate temporal analysis of five EXOSAT observations of the Seyfert 1 galaxy NGC 6814 covering about 2 yr. As firstly reported by Mittaz & Branduardi-Raymont (1989), the power spectrum of the longest (~1 d) observation is characterized by two major components: a low frequency noise which can be described, in the …