Search Publications

A study of interstellar absorption at high galactic latitudes. I. Highly ionized gas.

Pettini, M.; West, K. A.

IUE interstellar absorption line data for C IV, Si IV, N V and Fe II, in a sample of 24 distant, early-type stars at high galactic latitudes, are analyzed with other published results in order to study the distribution and physical conditions of highly ionized gas in the halo of the Galaxy. The C IV and Si IV lines, which are detected in front of …

The remarkable spectrum of some material ejected by eta Car.

Davidson, K.; Gull, T. R.; Walborn, N. R.

Some of the outer condensations of the very massive star Eta Carinae have emission-line spectra which convey clues to the nature of the star from which they were ejected. Ground-based spectrograms as well as ultraviolet IUE data on the brightest such condensation is described. Excess nitrogen presumably resulting from the C/N/O cycle implies that …

High-velocity winds from a dwarf nova during outburst.

Mason, K. O.; Cordova, F. A.

An ultraviolet spectrum of the dwarf nova TW Vir during an optical outburst shows shortward-shifted absorption features with edge velocities as high as 4800 km/s, about the escape velocity of a white dwarf. A comparison of this spectrum with the UV spectra of other cataclysmic variables suggests that mass loss is evident only for systems with rela…

H2 fluorescence spectrum from 1200 to 1700 A by electron impact - Laboratory study and application to Jovian aurora

Gladstone, G. R.; Yung, Y. L.; Ajello, J. M. +2 more

International ultraviolet explorer spectroscopy of hot stars in the LMC and SMC : the SMC extinction law, stellar flux distributions, and details of the stellar winds.

Hutchings, J. B.

IUE high- and low-dispersion spectral observations of hot stars in the Small Magellanic Cloud and Large Magellanic Cloud are presented. The extinction curve for the SMC derived from the data is much steeper in the UV than those of the LMC or the Galaxy. Based on stellar continuum data, stellar temperatures in the Magellanic Clouds are found to be …

The UV spectra of nearby white dwarfs and the nature of the local interstellar medium.

Kondo, Y.; Bruhweiler, F. C.

Detailed results from analysis of the IUE ultraviolet data obtained in the directions of the white dwarfs G191-B2B, W1346, HD 149499B, and Sirius B are presented. It is found that the sun is embedded in a low-density cloud extending to about 2-3 pc in most directions, with some evidence suggesting that the sun may be near the edge of the cloud. Th…

On the reality of a boundary in the H-R diagram between late-type stars with and without high temperature outer atmospheres.

Stencel, R. E.; Linsky, J. L.; Simon, T.

The Linsky-Haisch hypothesis (1979) that a boundary exists in the H-R diagram separating yellow giants from red giants and supergiants is tested. IUE 1150-2000 A low-resolution spectra of 10 stars chosen to constitute a reverse bias sample are presented and discussed. Despite the bias, weak C IV emission indicative of high-temperature plasma was o…

IUE observations of NGC 4649, an elliptical galaxy with a strong ultraviolet flux.

Capaccioli, M.; Oke, J. B.; Bertola, F.

As in the previously studied elliptical galaxies, the flux f(lambda) in NGC 4649 has a minimum at 2500 A followed by a rapid increase towards shorter wavelengths. In NGC 4649, the flux level of this rising branch is the highest so far observed and seems not to be correlated with the luminosity or activity in the galaxy. The excess shortward of 400…

The ultraviolet spectrum of the Crab nebula.

Davidson, K.; Gull, T. R.; Kafatos, M. +6 more

Ultraviolet spectroscopy of the Crab Nebula done by the International Ultraviolet Explorer satellite is described, and an estimate of the carbon abundance is made, noting data reduction to remove spectral defects caused by radiation hits. The important C IV 1549, He II 1640, and semiforbidden C III 1908 emission line intensities were measured and …

Ultraviolet observations of stellar chromospheric activity.

Raymond, J. C.; Dupree, A. K.; Hartmann, L.

A survey is presented of chromospheric and transition region (TR) line emission in late-type stars obtained with the IUE satellite. A wide variation in TR emission (ions formed near T = 100,000 K) at a given position in the H-R diagram is found, contradicting theories that incorporate only acoustic energy generation and deposition. The behavior of…