Search Publications
A Determination of the Basic Atmospheric Parameters of phi Cassiopeiae
Rosenzweig, Patricia; Anderson, Lawrence
By constructing non-LTE spherical model atmospheres, we have calculated a theoretical distribution of the emergent radiation that best matches the observed distribution of the supergiant Phi Cas, and so derived its effective temperature, surface gravity, and radius. Since Phi Cas is very likely a member of the open cluster NGC 457, we made extinct…
Ultraviolet and Optical Studies of Binaries with Luminous Cool Primaries and Hot Companions. IV. Further IUE Detections
Parsons, Sidney B.; Ake, Thomas B.
We have obtained IUE spectra for 31 middle and late-type giant and supergiant stars whose TD-1 fluxes or ground-based spectra indicate the presence of a hot component, or whose radial velocities indicate an unseen component. Stellar components earlier than type F1 were detected in 22 cases. While 20 of the hot secondaries are seen weakly in optica…
Detection of Far-Ultraviolet High-Excitation Line Emission and Lyman- beta Absorption in the Gravitational Lens Q0957+561
Kondo, Y.; Bruhweiler, F. C.; Michalitsianos, A. G. +7 more
Test runs with a new data processing software system on archival spectra obtained by the International Ultraviolet Explorer (IUE) reveal high-excitation emission lines in the gravitationally lensed binary quasar 0957+561. The lines of O VI λλ1031,1037 and S VI λ2933,945 are readily seen in a single 390 minute, low-dispersion IUE exposure, when cal…
Hubble Space Telescope Spectra of the Phase-modulated Wind in the SMC O+WR Binary R31
Bianchi, L.; Hutchings, J. B.; Morris, S. C.
We present HST/GHRS profiles of C IV 1500 A at conjunction phases 0.21, 0.26, and 0.72 of the 6.5 day O6+WN3 binary R31 in the SMC. We also use IUE archival data covering other orbital phases, There are strong changes in the line profile, depending on the line of view through an ionization bubble near the WR star. We fit a model for the stellar wi…
High-Speed Ultraviolet Photometry of HD 60435
Dolan, J. F.; Nelson, M. J.; Percival, J. W. +5 more
We present the first high-speed ultraviolet photometry of an oscillating Ap star, HD 60435. After removing known orbital effects related to the Hubble Space Telescope, we confirm the presence of a strong pulsation period at a frequency of 123.70 cycles per day. In addition, we find significant amplitude modulation of this frequency that we suggest…
A BBXRT Observation of the High-Luminosity Quasar H1821+643
Yaqoob, T.; Mushotzky, R. F.; Weaver, K. A. +3 more
We present the results of an observation of the high-luminosity quasar H1821+643 with the Broad-Band X-Ray Telescope (BBXRT) performed in 1990 December. The 2-10 keV flux and power-law spectral index are found to be consistent with previous values obtained by EXOSAT and Ginga which indicates that the medium-energy continuum has remained steady for…
An IUE Search for Star Formation in Ellipticals with Gaseous Disks
Renzini, Alvio; Burstein, David; Bertola, Francesco +1 more
New IUE observations are presented of NGC 5077, an elliptical galaxy known to have a Hα bright gaseous disk in its central region. The ultraviolet spectral energy distribution of NGC 5077 is compared to those of the bulges of two galaxies, M31 and NGC 3115, that are of similar Mg_2_ absorption-line strength and are known not to contain obvious gas…
Deflection of Light by the Earth
Gould, Andrew
General relativity predicts that light rays are deflected by gravitational fields. This effect has been observed with various degrees of precision on distance scales from 10 exp 11 to 10 exp 23 cm and on mass scales from 10 exp -3 to 10 exp 13 solar masses. The Hipparcos satellite can detect deflection of light by the earth, and can thereby extend…
Goddard High-Resolution Spectrograph Observations of Narrow Discrete Stellar Wind Absorption Features in the Ultraviolet Spectrum of the O7.5 III Star XI Persei
Ebbets, Dennis C.; Bolton, C. T.; Shore, Steven N. +2 more
We report the observation of transient narrow absorption components (NACs) in the stellar wind of the O giant Xi Per. Two sets of GHRS observations of the Si IV ultraviolet resonance doublet have been obtained. These features are extremely weak, with column densities of approximately 10 exp 12/sq cm and optical depths of order 0.1. The features ar…