Search Publications
Chromospheric-Coronal Activity at Saturated Levels
Walter, Frederick M.; Vilhu, Osmi
High-resolution IUE observations of Mg II emission lines in W Ursae Majoris were obtained. In addition, estimates of the Mg II emission for other F-type contact binaries were obtained using archival high-resolution k line spectra and some nonstandard methods; the available data were compiled for Mg II, C IV, and X-ray emission in main-sequence F, …
Ultraviolet observations of cataclysmic variables : the IUE archive.
Verbunt, F.
A comparative study of the ultraviolet properties of cataclysmic variables is made on the basis of the IUE data archive. The reddening to 51 systems is determined from the 2200 Å feature. The spectral flux distribution of cataclysmic variables does not depend on system type, orbital period or (for dwarf novae) average length of interval between ou…
Highly Ionized Interstellar Gas Located in the Galactic Disk and Halo
Savage, Blair D.; Massa, Derck
High-resolution IUE absorption line spectra have been obtained for 40 distant stars in order to study the distribution of interstellar H I, Si IV, C IV, and N V in the Galactic disk and lower halo. Respective midplane densities of 2 x 10 to the -9th, 7 x 10 to the -9th, and 3 x 10 to the -9th are found for Si IV, C IV, and Ni V. Both column densit…
Magnetic structure in cool stars. XII - Chromospheric activity and rotation of giants and dwarfs
Rutten, R. G. M.
The relation between the Ca II H and K line-core flux density and rotation rate is studied for 313 F- to M-type stars ranging in luminosity class from II-III to V. The activity-rotation relation for Ca II is compared with similar relations for Mg II and soft X-rays. Dwarfs and the majority of the giants studied follow the same color-dependent rela…
The Planetary Nebula NGC 3918
Harrington, J. P.; Walsh, J. R.; Barlow, M. J. +1 more
A detailed study of the planetary nebula NGC 3918, based on UV, optical, and radio observations, is presented. The central star has a predicted V magnitude of 14.6 and a luminosity of 6000 solar luminosities for a distance of 1.5 kpc. A contour map of the nebula in H-beta light is given. Velocity profiles of forbidden O II optical lines show that …
X-Ray Spectra of PG Quasars. II. The X-Ray--Ultraviolet Excess of PG 1211+143
Elvis, Martin; Green, Richard F.; Bechtold, Jill +2 more
Observations of the quasar PG 1211 + 143 are presented and its continuum is modelled in terms of an accretion disk and an underlying power law. The X-ray spectrum in the Einstein imaging proportional counter band is well described by a power law with the very steep spectral index 2.2 + or - 0.4. The overall continuum spectral energy distribution c…
The progenitor of SN1987A
Panagia, N.; Talavera, A.; Clavel, J. +6 more
One of the reasons why the bright supernova SN1987A is of such importance is the fact that its proximity would allow for the first time, the identification of a supernova progenitor star. Attempts to establish which star was the progenitor have led to uncertainties, however. Here we use spatial and spectroscopic information from International Ultr…
Rotational modulation and flares on RS CVn and BY DRA stars. III. IUEobserations of V711 Tau = (HR 1099), II Peg and AR Lac.
Doyle, J. G.; Linsky, J. L.; Simon, T. +8 more
The authors present observations of three RS CVn stars, which were obtained over the stellar rotation cycles with the IUE satellite. Emission lines from high-temperature transition regions and chromospheres analogous to those observed in the solar spectrum were observed. However, the stellar line surface fluxes are hundreds of times the solar valu…
IUE Observations of Comet p/ Halley - Evolution of the Ultraviolet Spectrum Between 1985SEP and 1986JUL
Feldman, P. D.; A'Hearn, M. F.; Schleicher, D. G. +13 more
The ultraviolet spectrum of comet P/Halley (1982 i) was monitored with the International Ultraviolet Explorer (IUE) satellite observatory between 1985 September 12 and 1986 July 8 (r < 2.6 AU pre- and post-perihelion) at regular time intervals except for a two-month period around the time of perihelion. A complete characterization of the UV spe…
A Detailed Study of the C IV lambda 1550 Line Profile and Adjacent Spectral Features in NGC 4151 from 1978 to 1983
Perola, G. C.; Altamore, A.; Boksenberg, A. +7 more
The 1450 - 1720 Å spectral region of NGC 4151 is analyzed by means of Gaussian decomposition for 69 different epochs, from early 1978 to the end of 1983. The C IV λ1550 emission profile is well represented by a core, whose full width at half-maximum varies between 2600 and 5500 km s-1, and an ultrabroad component (14,600 km s-1