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Deviation from the Wilson-Bappu relationship in faint red dwarf stars.
Carlsson, M.; Engvold, O.; Elgaroy, O.
New observations of the Mg II h and k lines on red dwarf stars have been carried out with the International Ultraviolet Explorer observatory. It is found that several of the dwarf stars in the sample have Mg II h and k lines which are narrower than expected from the Wilson-Bappu relationship, that is established for stars brighter than M(v) about …
Activity in late-type stars. VI. Optical photometry and UV spectroscopy of the active dMe star, FK Aquarii in late 1983.
Lyons, M. A.; Butler, C. J.; Byrne, P. B.
Optical photometry and UV spectroscopy are reported for the flare/BY Dra star FK Aqr from 1983. These data are used to derive the rate of optical energy release in U-band flaring and compare it to four previous epochs. No conclusive evidence of any variation in this rate over an 8-yr interval has been found. No measurable BY Dra variations were pr…
WW Horologii : revised period and X-ray light curve.
Tagliaferri, G.; Beuermann, K.; Giommi, P. +2 more
An improved orbital period of the eclipsing AM Herculis binary WW Hor is reported, which allows the relative phasing of 1983 EXOSAT X-ray and the 1986-89 optical light curves to be established. It is found that X-rays and optical cyclotron continuum are produced by the same accreting pole on the magnetic white dwarf. In 1984, WW Hor was not detect…
Particle observations by EPA/EPONA during the outbound pass of Giotto from comet Halley and their relationship to large scale magnetic field irregularities.
Neubauer, F. M.; Ip, W. -H.; Daly, P. +5 more
The acceleration processes producing spikes seen superimposed on the general intensity time profile of energetic particles obtained with EPA/EPONA during the outbound pass of Giotto on 14/15 March 1986, are studied using complementary magnetic field data. Three different types of spikes were identified. Evidence for the ion pick-up process and pro…
Stellar Mass Loss in Late B-Type Supergiants
Dufton, P. L.; Bates, B.; Gilheany, S. +1 more
A study using archive IUE data of time-varying mass loss has been carried out for a sample of 12 supergiants in the spectral range B5–B9. Additionally dedicated IUE velocity-time observations of 'discrete absorption components' (DAC) in the UV resonance lines have been made for one of the stars (βOri), while optical data obtained for this star sho…
Chromospheric Variability of M Giant Semiregular Variables
Johnson, Hollis R.; Eaton, Joel A.; Cadmus, Robert R., Jr.
The results of monitoring the chromospheric emission from three M giant semiregular variables, W Cyg, NU Pav, and Theta Aps at low dispersion with the IUE satellite are reported along with high-dispersion IUE spectra for R Lyr and Delta(2) Lyr. The chromospheric emission is variable in all of the first three stars, and the Mg II strength generally…
Model Atmosphere Analysis of the DZ White Dwarf K789-37
Koester, D.; Kilkenny, D.; Wegner, G.
This paper presents new observations and an analysis using model atmosphere techniques of the recently discovered DZA white dwarf K789 - 37. The effective temperature derived is 9500 + or - 500 K. Abundances are determined for the elements hydrogen, magnesium, calcium, and iron, as well as upper limits for carbon and silicon. The abundances are ve…
Ephemerides of the 48 HIPPARCOS minor planets for the year 1991
Bec-Borsenberger, A.
To be observed by Hipparcos, the position of each object has to be known with an accuracy of 1 arcsecond and its magnitude with an accuracy of 0.5 mag. Therefore, the orbital elements of 48 selected minor planets of the Hipparcos mission, have been improved in order to extrapolate their ephemerides with the accuracy required. These ephemerides for…
The Changing Soft X-Ray Lightcurve of the Am-Herculis System Mr-Serpentis = PG:1550+191
Stella, L.; Osborne, J. P.; Angelini, L.
We report the first soft X-ray light curves of the AM Her system MR Ser, all obtained within a 4-month interval in 1984. The source was serendipitously detected on three occasions by the EXOSA T low-energy telescope, and one observation was made in which MR Ser was the target. MR Ser was probably in a high optical state throughout, although it was…
FG Sagittae: No Hot Companion?
Feibelman, Walter A.; Bruhweiler, Frederick C.
The nucleus of the planetary nebula He 1-5 (= PK 60 -7 deg 1), the variable star FG Sge, was observed with the SWP camera of the International Ultraviolet Explorer satellite to detect a hot companion of the star, if such a companion exists. The observation found no evidence for the existance of a hot companion in the 1200-2000 A range of the SWP c…