Search Publications
Internal structure and polarization of the optical jet of the quasar 3C273
Mackay, C. D.; Thomson, R. C.; Wright, A. E.
THE extragalactic radio source 3C273 was the first quasar to be identified1, and remains one of the nearest and most luminous quasars known. In radio images2-4, it appears as a bright, point-like nucleus from which emerges a single large jet; the jet is also apparent in optical images5-8, but the relatively poor re…
Possible cataclysmic variable in the core of the globular cluster 47 Tucanae
Ferraro, Francesco R.; Paresce, Francesco; de Marchi, Guido
SEVERAL globular clusters have low-luminosity X-ray sources at their cores1-3, of which X0021.8-7221 in 47 Tucanae (NGC104) is one of the brightest. The nature of these sources is a mystery, and attempts to detect optical counterparts have been frustrated by the overcrowding of stars in cluster cores. The resolution of ground-based obse…
The O/C abundance ratio in absorbing gas clouds at high redshift
Clavel, J.; Reimers, D.; Vogel, S. +5 more
THE intrinsic extreme ultraviolet (EUV) spectrum of quasars, in which spectral lines of He and CNO ions should appear, is in most cases strongly absorbed by the hydrogen Lyman continuum of intergalactic matter at cosmological distances. The bright quasar HS1700 + 6416 (at redshift z = 2.72), from the Hamburg survey1, is a fortuitous exc…
Negative ions in the coma of comet Halley
Chaizy, P.; Anderson, K. A.; Reme, H. +8 more
IN March 1986, the Giotto spacecraft encountered comet Halley, approaching to within ~600 km of the nucleus. Results from this encounter have shown that the inner coma contains a mixture of cometary neutral gas and dust, thermal ions and electrons, fast cometary pick-up ions, and decelerated solar-wind ions and electrons, as well as fast neutrals<…
Blue stragglers in the core of the globular cluster 47 Tucanae
Boksenberg, A.; Barbieri, C.; Weigelt, G. +18 more
High-resolution observations of the core of the globular cluster 47 Tucanae with the Faint Object Camera on the Hubble Space Telescope reveal a high density of 'blue straggler' stars, occupying the upper end of the main sequence from which all stars in the cluster should have long since evolved. Their presence in the dense core supports the hypoth…
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…
Probable detection of organic-dust-borne aromatic C3H3+ ions in the coma of comet Halley
Anderson, K. A.; Reme, H.; Korth, A. +9 more
The heavy-ion analyser PICCA1,2 on the Giotto spacecraft was used to determine the composition and energy distribution of positively charged ions in the coma of comet Halley. Here we argue that the distinct peak observed at mass 39 AMU is due to the aromatic cation C3H3+ (cyclopropenyl). Laboratory mass …