Search Publications
The Giotto dust impact detection system
McDonnell, J. A. M.
The dust impact detection system (DIDSY) comprises six independent subsystems with the primary aim of registering the impacts of all particulates of significant mass incident on the Giotto probe during the post-perihelion encounter with comet Halley in 1986. Mounted on Giotto's front dust shield, the detectors determine the mass distribution of th…
Are There Stellar Winds in the Hot Stars of M31?
Massey, Philip; Bianchi, L.; Hutchings, J. B.
Results are reported of 16 hr exposures with the IUE satellite of two stars in M31. Ground-based spectra indicate these stars to be of type about O6 and WN 7. The UV spectra have good signal but are conspicuously different from Galactic stars of their type. Specifically, no line emission is seen in either star, resonance absorption lines are very …
Mass to Line Strength Relations from IUE Spectra of Early-Type Stars
Sekiguchi, Kazuhiro; Anderson, Kurt S.
An extensive survey of the 1200 - 1900 Å region in OB type stellar spectra obtained from the IUE archives has been used to establish line-strength versus spectral-type relationships. One hundred and sixty-three low-resolution IUE spectra of 124 well-classified O3 to B5 stars were examined. The authors confirm earlier results that the equivalent wi…
The Properties of OB Supergiants in the Large Magellanic Cloud. I. Energy Distributions of 10 B Supergiants
Fitzpatrick, Edward L.
It is demonstrated here that line-blanketed, LTE plane-parallel model atmosphere calculations provide excellent fits to the energy distributions from the ultraviolet through the visual ranges of B supergiants in the LMC. The models are computed using the atmosphere program of Kurucz (1979) but have been constructed with lower gravities than were c…
Simultaneous Multifrequency Observations of Markarian 421
Brodie, Jean; Bowyer, Stuart; Tennant, Allyn
The highly variable BL Lacertae object Mrk 421 has been observed simultaneously in the radio, optical, ultraviolet, and X-ray bands over a period of 4 days in early 1984 December and once again in early 1985 January. Using the EXOSAT observatory, the authors found that during this time the 2 - 10 keV flux dropped by a factor of 8, whereas the 0.1 …
The stellar winds of early-type stars in the Small Magellanic Cloud.
Prinja, Raman K.
Low-resolution IUE spectra are used to investigate stellar winds of early-type stars in the Small Magellanic Cloud (SMC). Model profiles are used to fit well developed P Cygni doublets noted in 25 main-sequence, giant, and supergiant stars. Terminal velocities in the SMC are found to be, generally, up to a factor of 2 lower relative to galactic O …
Spectropscopic Observations of the Symbiotic Binary RW Hydrae
Fernandez-Castro, Telmo; Kenyon, Scott J.
Ultraviolet/optical spectrophotometry and infrared photometry show that the symbiotic binary RW Hya is comprised of an M giant (with L of about 1000 solar luminosities) and a compact object (with L of about 200 solar luminosities) which resembles the central star of a planetary nebula. The luminosity of the hot component is produced by a nuclear s…
Ultraviolet and Optical Observations of AG Draconis
Lutz, J. H.; Lutz, T. E.; Dull, J. D. +1 more
IUE satellite observations and ground-based spectroscopic observations of the yellow symbiotic star AG Dra obtained at irregular intervals from 1975 to 1984 are presented. No forbidden lnes are observed in the optical, indicating a high density. The hydrogen emission lines often show a second blueshifted component that is not as strong as the main…
A pulse timing study of the X-ray pulsar 4U 1145-619.
Warwick, R. S.; Cook, M. C.
EXOSAT observations of the X-ray pulsar 4U1145-619, which is known to exhibit X-ray outbursts on an apparently regular 187-day cycle, have revealed a rapid decrease in the pulse period during the outburst states, whereas on longer time-scales the pulse period is found to be stable. The X-ray luminosity is too low, even during outburst, to account …
EXOSAT observations of the X-ray source in M 15.
Fabian, A. C.; Tennant, A. F.; Redfern, R. M. +2 more
The results from two long Exosat observations of the X-ray source in the globular cluster M15 (NC 7078), totalling approximately 1 d and separated by 100 d, are reported. Variability is detected on timescales down to 250 s, but no variations attributable to an eclipse were observed, which is surprising in view of the large fluctuations reported by…