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Comet P/Encke's Nongravitational Force

A'Hearn, Michael F.; Schleicher, David G.

A nearly direct measurement of the nongravitational force on a cometary nucleus is presented. IUE spectra of comet P/Encke show significant Greenstein effects even when centered on the nucleus. These imply net heliocentric components of outflow of 1.6 and 0.3 km/s for the OH radicals before and after perihelion near r = 0.8 AU. This implies a larg…

Spectroscopic binary orbits from ultraviolet radial velocities. Paper : AO Cassiopeiae.

Stickland, D. J.; Lloyd, C.

Ultraviolet and Radio Flares from UX ARIETIS and HR 1099

Willson, Robert F.; Lang, Kenneth R.

Simultaneous observations of the RS CVn systems UX Ari and HR 1099 with the IUE satellite and the VLA are presented. Flaring activity is observed at ultraviolet wavelengths with the IUE when none is detected at radio wavelengths with the VLA. Radio flares with no detectable ultraviolet activity have also been observed. Thus, flares in the two spec…

Recent Unusual Activity in the Be Star FY Canis Majoris

Peters, Geraldine J.

Unusual activity observed in the circumstelar envelope of FY CMa during April-May, 1987 is reported. Nightly CCD observations from April 16-20 revealed an invariant H-alpha emission feature and a simple absorption profile for He I 6678 with very weak double emission components. Similar observations on May 2, however, showed that the V lobe of the …

Analysis of C II resonance lines in some main sequence early-type stars.

Cugier, H.; Hardorp, J.

An analysis of C II resonance lines at 1335 Å in eight main-sequence stars of spectral types A0 to B3 is performed using IUE archival data released for general use. In order to interpret the observed spectra, both LTE and non-LTE line profiles were computed. In stars with low rotational velocities (Vega, π Cet, τ Her and ι Her) the authors obtaine…

Optical and Ultraviolet Activity in RT Lacertae During 1985 and 1986

Huenemoerder, David P.

Continued monitoring of optical spectra of RT Lac, a peculiar RS CVn system, showed a large range of activity in the H-alpha line. At times, there was no excess emission or absorption, and at others, much. During active times, the excess emission varied greatly with phase and seemed to come from an extended region. Two UV observations, taken conte…

A Search for the Binary Companion of Polaris

Evans, Nancy Remage

Polaris has a spectroscopic orbit determined from an extensive series of observations as well as a more uncertain astrometric orbit. The determination of its mass and evolutionary state is of considerable interest because it is a low-amplitude classical Cepheid with unusual period and amplitude variations. In this study, IUE spectra are investigat…

Chromospherically Active Stars. IV. HD 178450=V478 LYR: an Early-Type BY Draconis Type Binary

Fekel, Francis C.

The variable star HD 178450 = V478 Lyr is a chromospherically active G8 V single-lined spectroscopic binary with a period of 2.130514 days. This star has strong ultraviolet emission features and a filled-in Hα absorption line which is variable in strength. It is classified as an early-type BY Draconis system and is similar in many respects to the …

Search for Linear Polarization in Gamma-Ray Sources: Possible Evidence for the VELA Pulsar

Caraveo, P. A.; Bignami, G. F.; Mitrofanov, I. +1 more

The use of the azimuthal distribution of planes containing e(+)/e(-) pairs from high-energy photon materialization to investigate the nature of gamma-ray sources is discussed. Analytical work done on COS B data for bright COS B sources (Vela, Crab, and Geminga) and for a reference background region is presented along with results which are indicat…

A sudy of the continuum flux and the line structure in the IUE spectrum of beta Lyrae.

Sahade, J.; Hack, M.; Engin, S. +5 more

A study of the available archival IUE images of Beta Lyrae has led to the following results: (1) for lambda in the range of 1250 - 1500 A, the eclipse depth at second conjunction is slightly larger than the eclipse depth at primary conjunction; they are equal at about 1670 A; (2) the profiles of the resonance lines of SiIV (and the same seems to b…