Search Publications
Constraints on the mass-radius relation of the neutron star in 4U 1746-37/NGC 6441.
van Paradijs, J.; Lewin, W. H. G.; Vacca, W. D. +4 more
An analysis of 12 hours of continuous EXOSAT observations of 4U 1746-37 in NGC 6441, obtained between September 9 and 10, 1985, puts constraints on its mass-radius relation. The spectral shape of the persistent X-ray flux is well fitted by a thermal bremsstrahlung spectrum, with a kT temperature varying between 7.5 and 9.8 keV, and an interstellar…
Star formation in nuclei of SO/E galaxies.
Rocca-Volmerange, B.; Guiderdoni, B.
Spectra of nuclei for some lenticular and elliptical galaxies observed from the IUE satellite in the far-UV light are analyzed with the help of the IUE spectral atlases using an almost similar resolution for galaxies and stars, down to about 8A for a significant signal/noise ratio. In the 2500A-3150A wavelength range, all gas-poor galaxies show 'r…
EXOSAT Observations of 4U/MXB 1636-53: On the Relation between the Amount of Accreted Fuel and the Strength of an X-Ray Burst
van Paradijs, J.; van der Klis, M.; Lewin, W. H. G. +4 more
During EXOSAT observations of 4U/MXB 1636-53 in 1985 August, three bursts were observed in 6 hr and 24 bursts in 79 hr of uninterrupted observing. The persistent X-ray flux varied by about a factor of 2.4, the burst intervals by a factor of 24 (from 35 minutes to 14 hr), and the integrated burst fluxes (the burst fluences), and burst peak fluxes b…
The SN Stars: Magnetically Controlled Stellar Winds Among the Helium-Weak Stars
Shore, Steven N.; Brown, Douglas N.; Sonneborn, George
The authors report observations of magnetically controlled stellar mass outflows in three helium-weak sn stars: HD 21699 = HR 1063, HD 5737 = α Scl, and HD 79158 = 36 Lyn. IUE observations show that the C IV resonance doublet is variable on the rotational timescale but that there are no other strong-spectrum variations in the UV. Magnetic fields, …
The Giotto three-dimensional positive ion analyser
Coates, A. J.; Winningham, J. D.; Borg, H. +9 more
An instrument to measure the three-dimensional energy distribution of positive ions in order to study the interaction between the solar wind and ionized Halley cometary particles was designed. Two sensors measure the distribution from 10 eV to 20 keV once per spacecraft spin and the distribution from 90 eV to 90 keV, with coarse mass discriminatio…
Magnetic structure in cool stars. XIII - Appropriate units for the rotation-activity relation
Rutten, R. G. M.; Schrijver, C. J.
The paper compares relations between coronal and chromospheric emissions, and between activity and stellar rotation, in which the radiative emissions that measure the magnetic activity of cool stars are expressed in different units. The surface flux density appears to be the most suitable unit in which to express the radiative emission measuring s…
Photometric properties of SN 1987A and other sources in the same field.
Panagia, N.; Clavel, J.; Wamsteker, W. +5 more
The authors find that the UV flux of SN 1987A declines since the very first IUE observation at a rate which is faster at shorter wavelengths while the emission around 5100 Å increases slowly but steadily with time. Thus, the UV radiation dominates the overall emission at early phases but becomes completely negligible at later phases. Such an evolu…
EUV photometry of DA white dwarfs with EXOSAT.
Jordan, S.; Koester, D.; Brunner, H. +1 more
The authors present EXOSAT EUV observations for 9 white dwarfs of spectral type DA. These are analysed together with other observational data from the literature using theoretical model atmospheres. For 8 objects He/H abundance ratios and interstellar hydrogen column densities are obtained. The data for HZ 43 seem to contradict recent results of o…
High-Energy Gamma Rays Probing Cosmic-Ray Spectral Differences thoughout the Galaxy
Bloemen, J. B. G. M.
Detailed spectra of the Galactic γ-ray emission (50 MeV-6 GeV) are derived from a combination of all the observations obtained with the COS-B satellite. These spectra indicate that the cosmic-ray (CR) proton spectrum is on average flatter in the outer Galaxy than in the inner Galaxy and locally by approximately ∝ E0.4, and maybe more, s…
The (C III lambda 1909/Si III lambda 1892) Ratio as a Diagnostic for Planetary Nebulae and Symbiotic Stars
Feibelman, Walter A.; Aller, Lawrence H.
Suitable IUE archival material on planetary nebulae has been examined to determine the log R /F(lambda 1909 C III)/F(lambda 1892 Si III)/ as a discriminant for distinguishing planetary nebulae from symbiotic stars and related objects. The mean value of log R for 73 galactic planetaries is 1.4, while that of extragalactic planetaries appears to be …