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CN Anomalies in Extremely Metal-Deficient Red Giants
Twarog, Bruce A.; Anthony-Twarog, Barbara J.; Shawl, Stephen J.
New photometric and UV spectroscopic data for the metal-deficient red giants CD -38 deg 245 and BD -18 deg 5550 are presented and discussed in light of recently noted photometric anomalies. From the IUE spectra it is aparent that the UV excess found in BD -18 deg 5550 is not the result of a hot companion. The IUE spectra, in conjunction with other…
A VLA 3.6 Centimeter Survey of N-Type Carbon Stars
Brown, Alexander; Luttermoser, Donald G.
The results are presented of a VLA-continuum survey of 7 N-type carbon stars at 3.6 cm. Evidence exists for hot plasma around such stars; the IUE satellite detected emission lines of singly ionized metals in the optically brightest carbon stars, which in solar-type stars indicate the existence of a chromosphere. In the past, these emission lines w…
Astrometric Performance Characteristics of the Hubble Space Telescope Fine Guidance Sensors
Benedict, G. F.; Franz, O. G.; Hemenway, P. D. +10 more
Each of the three Fine Guidance Sensors for the Hubble Space Telescope constitutes a sixth science instrument to be used for astrometry. We detail the tests and results used in choosing one of the three sensors to be the prime astrometer. The Astrometry Science team has chosen Fine Guidance Sensor (FGS) 3. FGS 3 produces position measurements on a…
Possible First Detection of Ultraviolet Pulses from an Intermediate Polar: V603 Aquila
Udalski, A.; Schwarzenberg-Czerny, A.; Monier, R.
We report possible independent detection of a pulsation in the UV continuum radiation of the intermediate polar star, V603 Aql, at 2.2 sigma level. Since the period of the pulsation of 62.9 minutes is very close to the period of X-ray and optical modulations discovered earlier, its detection combined with previous data confirms reality of UV, X-ra…
Ulysses particle observations of the March 1991 solar flare events
Heras, A. M.; Forsyth, R.; Balogh, A. +4 more
We present observations of energetic ions from the COSPIN instrument on the Ulysses spacecraft at 2.5 AU during the March 1991 series of solar flare events. The intensity profiles observed during this sequence of events were affected both by the presence of interplanetary shocks and large-scale discontinuities in the magnetic field, the low-energy…
The Origin of the Far-Ultraviolet Continuum in Solar and Stellar Flares
Bromage, G. E.; Doyle, J. G.; Phillips, K. J. H.
A continuum in the far-ultraviolet region observed in IUE spectra of dMe stars in a flaring state is discussed and compared with that observed in solar flares. Similar continuous emission observed in solar flare far-ultraviolet spectra has been identified with neutral silicon recombination radiation excited by intense lines. This also appears to b…
Applications of the infrared flux method to 3 cool AP stars (78 Virginis, 52 Herculis A and CS Virginis) and comparison of their energy distributions to model atmospheres.
Monier, R.
The infrared flux method proposed by Blackwell and Shallis (1977) is used, along with a comparison of the observed energy distribution to model grids, in order to determine the fundamental parameters of three cool Ap stars: 78 Vir, 52HerA, and CS Vir. The degree to which their energy distributions can be reproduced using currently available model …
28. Tycho transit detection.
Wagner, K.; Hog, E.; Wicenec, A. +3 more
By means of some extracted parts of the raw countrates of the Tycho photomultipliers the method of detecting signals of stars and estimating their amplitudes and transit positions is described. The elimination of disturbances due to spikes with the help of sophisticated folding and background determination methods is presented.
Expected accuracy of the 1900-1990 earth orientation parameters in the HIPPARCOS reference frame
Vondrak, Jan; Feissel, Martine; Essaifi, Najat
Based on the space and time distribution of observations available over 1900-1990 for estimating the motion of the earth rotation axis in space and relative to the earth's crust, and universal time, we evaluate the accuracy of the earth orientation parameters in the framework of their global analysis in the Hipparcos reference frame currently unde…
The coronal-sounding experiment
Bird, M. K.; Asmar, S. W.; Volland, H. +3 more
The main science objective of the Ulysses Solar Corona Experiment is to derive the plasma parameters of the solar atmosphere using established coronal-sounding techniques. Applying appropriate model assumptions, the 3D electron density distribution will be determined from dual-frequency ranging and Doppler measurements recorded at the NASA Deep Sp…