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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…