Search Publications
Deviations from a uniform period spacing of gravity modes in a massive star
Aerts, Conny; Miglio, Andrea; Bloemen, Steven +13 more
The life of a star is dominantly determined by the physical processes in the stellar interior. Unfortunately, we still have a poor understanding of how the stellar gas mixes near the stellar core, preventing precise predictions of stellar evolution. The unknown nature of the mixing processes as well as the extent of the central mixed region is par…
Discovery of molecular hydrogen in a high-velocity cloud of the Galactic halo
de Boer, K. S.; Grewing, M.; Richter, P. +4 more
The Milky Way's halo contains clouds of neutral hydrogen with high radial velocities which do not follow the general rotational motion of the Galaxy. Few distances to these high-velocity clouds are known, so even gross properties such as total mass are hard to determine. As a consequence, there is no generally accepted theory regarding their origi…
A high deuterium abundance at redshift z = 0.7
Ferlet, R.; Vidal-Madjar, A.; Lemoine, M. +4 more
Of the light elements, the primordial abundance of deuterium relative to hydrogen, (D/H)p, provides the most sensitive diagnostic for the cosmological mass density parameter, ΩB. Recent high-redshift D/H measurements are highly discrepant, although this may reflect observational uncertainties,. The larger primordial D/H value…
Dust formation in Nova Cassiopeiae 1993 seen by ultraviolet absorption
Sonneborn, G.; Hauschildt, P. H.; Shore, S. N. +2 more
The clouds of gas in interstellar space also contain grains of dust, whose properties and origins have been the focus of debate for decades. Some dust formation has been assumed to take place in novae explosions1-5, as was first implied by the observation of a steep decrease in the amount of light emitted by the nova1,2 DQ He…
Spectral transformation of the unusual variable star MWC560 to resemble a nova
Sonneborn, George; Maran, Stephen P.; Oliversen, Ronald J. +1 more
MWC560 is an emission-line star catalogued1in 1943 and later described2 as an 'extraordinary symbiotic-like variable'. It was recently found3 to be undergoing a photometric and spectroscopic outburst. A dramatic change has occurred in the ultraviolet spec-trum of MWC560, so that it now closely resembles the spectru…
Detection of a stellar flare at extreme ultraviolet wavelengths
Bromage, G. E.; Barstow, M. A.; González-Riestra, R. +3 more
THE transition region between stellar chromospheres and coronae contains plasma at temperatures of 105-106 K, radiating predominantly at extreme ultraviolet (EUV) wavelengths (60-1,000 Å 0.012-0.2 keV). To understand the energy transport processes that maintain the corona, radiative losses from this region must be studied, pa…
Raman scattering as a diagnostic tool in the massive X-ray binary 4U1700 - 37
Hammerschlag-Hensberge, G.; Kaper, L.; Takens, R. J.
HD153919, an extreme Of star (spectral type O6.5Iaf+; ref. 1) has been identified as the optical counterpart of the 3.411-day eclipsing massive X-ray binary 4U1700 - 37 (ref. 2) by spectroscopic3-5 and photometric6 studies which revealed periodic optical variations in phase with the X-ray period. Here we report tha…
Detection of H3+ on Jupiter
Atreya, S. K.; Drossart, P.; Clarke, J. T. +9 more
SINCE their detection in the high latitudes of Jupiter, first by the Voyager Ultraviolet Spectrometer (UVS) experiment1,2, then by the International Ultraviolet Explorer (IDE) satellite3, the auroral particle precipitations have been associated with various phenomena in the jovian environment. In the magnetosphere, the H…
Deuterium content of the Venus atmosphere
Bertaux, J. -L.; Clarke, J. T.
THERE is no liquid water on Venus. The water vapour in its atmosphere would, if condensed, form a layer only 20 cm deep which means, in contrast to the 3-km-deep oceans that cover its sister planet Earth, that Venus is very dry indeed. It is not known with certainty whether Venus has lacked water since its formation, or if water once present has b…
Surficial textures of the Galilean satellites
Buratti, B. J.; Nelson, R. M.; Lane, A. L.
Knowledge of the textural characteristics of planetary surfaces is one of the objectives of remote sensing observations. The comparison of accurate photometric measurements with scattering models yields estimates of the compaction state of the optically active portion of the regoliths of airless bodies. We have analysed as a function of solar phas…