Search Publications
The "noisy" pulsar in HER X-1.
Belloni, T.; Kahabka, P.; Hasinger, G.
The results of a comparative analysis of coherent and noncoherent variations in the X-ray emission of Hercules X-1 are presented, based on Exosat archive data. In the broad band power spectrum of the source a strong noise component, variable with the 35-days cycle, is present. These changes, and the relation between the noise rms and the pulsed rm…
The Far Ultraviolet Spectrum of the 04V-F Star 9-SAGITTARII
Danezis, E.; Laskarides, P. G.; Theodossiou, E.
A detailed list of line identifications of the far UV spectrum of the O4V((f)) star 9 Sagittarii (HD 164794) in the wavelength range λλ1174-2000 Å is presented. The identification is based on two spectra recorded in 1981 (on 16 April—SWP 13729 and on 24 August—SWP 14805) by the International Ultraviolet Explorer (IUE). In the list many unclassifie…
A comparison between two strategies of data reduction for the Hipparcos project
Lattanzi, M. G.; Bucciarelli, B.; Sarasso, M. +2 more
Two different strategies for reducing HIPPARCOS data are directly compared and their respective impact on the final precision of the HIPPARCOS Catalog is evaluated. These strategies are the FAST (Fundamental Astronomy by Space Techniques) Consortium's Baseline and GLOBUS procedures. The Baseline is already operating on satellite data; GLOBUS was i…
Searching for the White Dwarf in Dwarf Novae
Mattei, Janet A.; Nelan, Edmund; Holm, Albert V. +1 more
AAVSO observations of dwarf novae were used to select targets in a search by the International Ultraviolet Explorer (IUE) satellite for their white dwarf components. Twelve of fourteen attempts caught the dwarf novae in quiescence. Lyman alpha absorption such as seen in white dwarf stars was found in three of the six observed systems, two of which…
Photomultiplier for optically probing Comet Halley
Llebaria, A.; Lamy, P.; Levasseur-Regourd, A. C. +7 more
A low mass eight-color channel photopolarimeter was developed for the Giotto spacecraft. Utilizing the spin of the spacecraft, a multichannel plate photomultiplier, and a unique optical design, the instrument required no moving parts to measure color and linear polarization. The photopolarimeter collected data as the spacecraft passed through the …
The missing UV absorption lines of NGC 4151.
Penston, M. V.; Snijders, M. A. J.; Leech, K. J.
In this paper we discuss new, near-simultaneous high-dispersion long- and short- wavelength International Ultraviolet Explorer (IUE) observations of the Seyfert galaxy NGC 4151. Previous observations revealed a narrow absorption system in Mg II not present in Lyα or C IV. The new observations confirm the presence of this system in Mg II and its ab…
Heating Mechanism(s) for Transition Layers in Giants
Bohm-Vitense, Erika; Mena-Werth, Jose
The emission-line fluxes of lines originating in the lower parts of the transition layers between stellar chromospheres and coronas are studied. Simon and Drake (1989) suspect different heating mechanisms for 'hot' and cool stars. Changes in the flux ratios for the C IV to C II emission lines support this suspicion. Large C IV/C II line flux ratio…
Ultraviolet Fe VII Absorption and Fe II Emission Lines of Central Stars of Planetary Nebulae
Cheng, Kwang-Ping; Feibelman, Walter A.; Bruhweiler, Frederick C.
The SWP camera of the IUE satellite was used in the high-dispersion mode to search for Fe VII absorption and Fe II high-excitation emission lines in five additional very hot central stars of planetary nebulae. Some of the Fe VII lines were detected at 1208, 1239, and 1332 A in all the objects of this program, LT 5, NGC 6058, NGC 7094, A43, and Lo …
Hipparcos: Revised mission overview
Perryman, M. A. C.
The Hipparcos astrometry satellite was launched on 8 August 1989, and after spacecraft and payload commissioning, commenced the routine data acquisition phase on 26 November 1989. Having failed to reach its planned geostationary orbit, major revisions in the mission operations had to be performed, although the impact on the final mission accuracie…
Erratic profiles of type II bursts of very low fluence from the rapid burster.
Lewin, Walter H. G.; van Paradijs, Jan; Lubin, Lori M. +2 more
Results are presented of approximately 17 hr of Exosat observations of the Rapid Burster in September 1985 during which about 541 type II bursts lasting less than 30 s were observed. Although these bursts are known to have an approximately time-invariant profile showing successive peaks in the burst's decay portion, most of the 20-s bursts at the …