Search Publications
The discovery of S2 in comet IRAS-Araki-Alcock 1983d
Feldman, P. D.; A'Hearn, M. F.; Schleicher, D. G.
Ultraviolet spectra of comet IRAS-Araki-Alcock 1983d, obtained with the International Ultraviolet Explorer spacecraft when the comet was only 0.032 AU from earth, show strong emission bands due to S2, the first detection of this species in an astronomical object. The spatial profiles imply that the S2 is released directly from the nucleus and has …
First observations of stellar coronal structure : the coronae of AR Lacertae.
Basri, G. S.; Walter, F. M.; Gibson, D. M.
In connection with the present investigation, X-ray, radio, and ultraviolet observations of AR Lacertae over one orbital cycle have been obtained. The X-ray light curve shows a deep primary minimum and a broad, shallow secondary minimum. The quiescent corona of the G2 IV component is small and asymmetric. This corona extends some 0.02 stellar radi…
Extreme variability in the Be-type, periodic recurrent X-ray transient AO538-66 : a highly eccentric interacting binary.
Howarth, I. D.; Charles, P. A.; Willis, A. J. +6 more
The recurrent X-ray transient sources represent a substantial class of galactic objects which are difficult to study extensively. They can be divided into two groups on the basis of their optical primaries, including the low-mass systems which are optically faint outside their outbursts, and those with high masses. White and Carpenter (1978) disco…
The distance, temperature, and luminosity of the hypergiant P Cygni (B1 Ia+).
Lamers, H. J. G. L. M.; Cassatella, A.; de Groot, M.
The basic parameters of P Cyg (B1 Ia+) are determined from a study of the overall energy distribution from 1150 A to 6 cm. The color excess of E(B-V) = 0.63 + or - 0.05 is derived from the strength of the interstellar Lyman-alpha line, from the spectral type, and from a comparison of the UV energy distribution with those of other supergiants. The …
The structure and emission spectrum of a nonradiative shock wave in the Cygnus Loop.
Gull, T. R.; Raymond, J. C.; Fesen, R. A. +1 more
The ultraviolet spectrum of a Balmer-line filament located just outside the main body of optical filaments in the Cygnus Loop confirms the nonradiative shock wave theory for its origin. This theory is extended to include the hydrogen two-photon continuum, and the possibility of slow electron-ion equilibration in the postshock gas is considered. Th…
Period-activity relations in close binaries.
Vilhu, O.; Rucinski, S. M.
The chromosphere transition region and coronal emissions of late spectral type main sequence stars with rotational periods short enough to bridge the gap between rapidly rotating single stars and contact binaries are analyzed. It is found that very active sample stars do not follow the scaling laws of Ayres et al. (1981) for line intensities origi…
A multifrequency study of star formation in the blue compact dwarf galaxy I ZW 36.
Thuan, T. X.; Viallefond, F.
Radio, near IR, optical, and UV observations of I Zw 36 = Mrk 209 = Haro 29 are reported. The H I distribution shows a core-halo structure, the core containing half of the mass and showing systematic motions; the halo is diffuse and contains several H I clumps. The visible star formation region is associated with the core but is shifted slightly w…
Episodic mass loss and narrow lines in Gamma Cassiopeiae and in otherearly-type stars.
Howarth, I. D.; Hammerschlag-Hensberge, G.; Barr, P. +1 more
High-resolution ultraviolet spectra obtained with the IUE of the B0.5 IVe star γ Cas have revealed conspicuous changes in the profiles of the resonance doublet lines of C IV, N V, and Si IV. In 18 out of the 28 available spectra, narrow absorption components of varying strengths are found at the blueshifted side of the rest wavelength. The central…
The ionization structure of planetary nebulae. III. NGC 7009.
Barker, T.
Barker has found (1980, 1982) that combined optical and ultraviolet observations in several different regions of one planetary nebula, NGC 6720, can be used both to estimate particularly reliable total elemental abundances and to learn more about the physical conditions in the nebula. It is important, however, that all the observations be made in …
Mass loss, levitation, accretion and the sharp-lined features in hot white dwarfs.
Kondo, Y.; Bruhweiler, F. C.
A study has been conducted of eight white dwarfs, including seven DA and one He-rich types. The study is based on high-resolution observations conducted with the aid of the International Ultraviolet Explorer. Four of the dwarfs show features related to heavy elements which are not interstellar in origin. It is tentatively suggested that, at least …