Search Publications

IUE Observations of PG 1115+080: The He i Gunn-Peterson Test and a Search for the Lensing Galaxy

Tripp, Todd M.; Green, Richard F.; Bechtold, Jill

We have obtained new IUE observations of PG 1115+080 (z_em_ = 1.722), the "triple quasar," in order to carry out the He I Gunn-Peterson test with greater sensitivity and to search for a Lyman-limit discontinuity which could reveal the redshift of the gravitational lens. We find that n_HE I_(z = 1.722) ~ 7x10^11^ h_100_ cm^-3^ at the 3 σ level. We …

The Evolution of Magnetic Activity on V711 Tauri and Evidence for a Significant Facular Contribution

Guinan, E. F.; Dorren, J. D.

The nature of the long-term evolution of magnetic activity in the RS CVn binary V711 Tauri is investigated using the complete set of available archival IUE SWP low-dispersion spectra of V711 Tau for the period covering August 1978 - December 1984. An analysis of the spectra confirmed the pattern of a long-term smooth variation of chromospheric and…

IUE and Einstein Survey of Late-Type Giant and Supergiant Stars and the Dividing Line

Maggio, A.; Vaiana, G. S.; Haisch, Bernhard M. +2 more

Results are presented on an IUE UV survey of 255 late-type G, K, and M stars, complementing the Maggio et al. (1990) Einstein X-ray survey of 380 late-type stars. The large data sample of X-ray and UV detections make it possible to examine the activity relationship between the X-ray and the UV emissions. The results confirm previous finding of a t…

Studies of H i and D i in the Local Interstellar Medium

Moos, H. W.; Murthy, J.; Linsky, J. L. +3 more

High-dispersion IUE spectra are presented of the hydrogen Ly-alpha chromospheric emission line of two nearby late-type stars, Capella and Lambda And. Both interstellar H I and D I Ly-alpha absorption can be seen against the chromospheric line, and the density, velocity dispersion, and bulk velocity of the gas in those lines of sight are derived. L…

High-Latitude SPOT and Plage Activity on the Rapidly Rotating M Dwarf Star Gliese 890

Young, Arthur; Skumanich, Andrew; MacGregor, Keith B. +1 more

Simultaneous time-resolved observations in broadband photometry and in H-alpha and near-UV spectroscopy are presented of Gliese 890, a single M dwarf of the BY Draconis type with the shortest known period of rotation among field stars of its type. The continuum light curves exhibit modulations characteristic of the presence of localized dark spot …

The Discovery of Strong Neutral Atomic Carbon Absorption Lines in the Spectrum of the DAQZ5 White Dwarf in the Ultra--Short-Period Dwarf Nova WZ Sagittae during Quiescence

Szkody, Paula; Sion, Edward M.; Leckenby, Henry J.

Coordinated Optical and Ultraviolet Observations of IM Pegasi

Huenemoerder, David P.; Buzasi, Derek L.; Ramsey, Lawrence W.

IUE spectra and optical observations of IM Peg obtained during the summers of 1985 and 1986 are analyzed. The modulations of the UV emission lines and the H-alpha, H-beta, and the CaII IR triplet (IRT) optical lines are examined. It is observed that: the UV emissin-line modulation increases as a function of height, H-alpha variability is related t…

H1722+119: A Highly Polarized X-Ray--selected BL Lacertae Object

Schwartz, D. A.; Tuohy, I. R.; Remillard, R. A. +2 more

We report the discovery of a 15th magnitude X-ray-selected BL Lacertae object as part of a program to identify X-ray sources observed by the Scanning Modulation Collimator experiment during the HEAO I all-sky survey. The BL Lac object, H1722+119, is a strong and persistent X-ray source originally discovered by Uhuru and located by the HRI instrume…

Chromospheres of Two Red Giants in NGC 6752

Smith, Graeme H.; Dupree, A. K.; Jordan, Carole +3 more

Two red giant stars, A31 and A59, in the globular cluster NGC 6752 exhibit Mg II (2800 A) emission with surface fluxes comparable to those observed among metal-deficient halo field giants, and among low-activity Population I giants. Optical echelle spectra of these cluster giants reveal emission in the core of the Ca II K (3933.7 A) line, and in t…

Period Measurements of the 50 Millisecond Pulsar PSR 0540-69 with the EXOSAT Satellite

Hasinger, Guenther; Oegelman, Hakki

The period of the 50 ms pulsar PSR 0540 - 69 in the Large Magellanic Cloud was determined using five separate X-ray observations with the Exosat satellite in the interval August 12, 1984 to June 30, 1985. Together with Einstein observations and contemporaneous optical data, the Exosat periods can be fitted well to a quadratic curve yielding a brak…