Search Publications
The expanding envelope of ζ Aurigae.
Baade, R.; Kirsch, T.
We redetermine the basic parameters of the circumstellar envelope of ζ Aur by means of the UV binary technique. The analysis consists of comparing IUE observations with theoretical profiles calculated with a newly developed 2-D radiative transfer code. We show that the B-type secondary causes an open HII region. The electron temperature and the io…
Evidence for ellipsoidal variations of the Be star binary HD 50123.
Sterken, C.; Vogt, N.; Mennickent, R.
On the basis of 8 years of photoelectric monitoring in the Stroemgren system we were able to establish that HD50123 is an interacting binary consisting of a B6Ve primary and an early K giant secondary which fills its Roche lobe. The orbital period is 28.601days. The secondary contributes considerably to the flux in the y and b bands, in which the …
A Far-Ultraviolet Flare on a Pleiades G Dwarf
Linsky, J. L.; Basri, G. S.; Antiochos, S. K. +9 more
The Hubble Space Telescope/Faint Object Spectrograph (HST/FOS) recorded a remarkable transient brightening in the C IV lambda lambda 1548,50 emissions of the rapidly rotating Pleiades G dwarf H II 314. On the one hand the 'flare' might be a rare event luckily observed; on the other hand it might be a bellwether of the coronal heating in very young…
An EXOSAT Detection of the Transient X-Ray Pulsar GRO J1008-57
Shrader, C. R.; Schultz, A. B.; Macomb, D. J.
The hard X-ray transient, GRO J1008-57, was discovered during a bright outburst in 1993 July by the Burst and Transient Source Experiment (BATSE) instrument on board the Compton Gamme-Ray Observatory (CGRO). There are no published reports of previous emission from this 93.6 sec X-ray pulsar. Recent optical results have suggested a Be star as the c…
Connection between X-Ray and Optical Variability in NGC 4151
Oknyanskij, V. L.
We have used long light curves in the X-ray (ARIEL V, EXOSAT, Ginga and others), UV (IUE), and optical (data of intensive ground-based monitoring) ranges of NGC 4151 to investigate connections between variations in these spectral fields. Applying Fourier (CLEAN algorithm) and modern cross-correlation analysis, we revealed the different character o…
Soft X-ray observations of EXO 2030+375
Mavromatakis, F.
The X-ray transient pulsar EXO 2030+375 was observed by ROSAT in November 1990 during the All-Sky survey. The observation took place very close to periastron passage and the source was clearly visible over an interval of two days. The average flux level suggests an active companion star although the ROSAT flux is lower than the observed flux in mo…
Ultraviolet variations in the spectrum of the visible central star of Abell 35.
Jasniewicz, G.; Lapierre, G.; Monier, R.
We report on simultaneous IUE and photometric observations carried out in March 1992 of the G8IV star BD-22 3467 located at the centre of the planetary nebula Abell 35. The main feature of the IUE low resolution spectra is a strong Mg II emission, which is common in fairly close binaries. Meanwhile no variations of the hot companion were detected …
A preliminary list of stars from TYCHO observations
Bastian, U.; van Leeuwen, F.; Petersen, C. +6 more
The final Tycho Catalog will be a major source of astrometric standard stars when it will be published, in 1997. While the Tycho positions with their full accuracy will only be available at the end of the data reduction, it is already possible to derive a preliminary list of about one million stars from the Tycho Input Catalogue (TIC) which have a…
Observations of the solar wind from coronal holes
Neugebauer, M.
The solar wind emanating from coronal holes (CH) constitutes a quasi-stationary flow whose properties change only slowly with the evolution of the hole itself. Some of the properties of the wind from coronal holes depend on whether the source is a large polar coronal hole or a small near-equatorial hole. The speed of polar CH flows is usually betw…
Transition in the X-Ray Light Curve of the AM Herculis System V834 Centauri (E1405-451): 1985--1986 EXOSAT Observations
Sambruna, Rita M.; Treves, Aldo; Maraschi, Laura +2 more
We analyze the EXOSAT observations of the AM Herculis system V834 Centauri (E1405-451), taken in 1985 March and 1986 August. Archival UV data, simultaneous with the 1986 observations, are also considered. The soft X-ray light curve has a double humped structure, with total eclipse at phi approximately 0.0. It differs significantly from that observ…