Search Publications
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…
An Ionized Accretion Disk in Cygnus X-1
Done, C.; Mulchaey, J. S.; Mushotzky, R. F. +1 more
Results of an analysis of archival Exosat and HEAO 1-A2 observations of Cyg X-1 are presented. It is found, in agreement with Ebisawa (1991), that the X-ray spectrum of Cyg X-1 exhibits a 'high-energy excess' above 8 keV, similar to that seen in Ginga spectra of AGN. It is shown, on the basis of a likelihood ratio test, that the data are significa…
Correlated Hard X-Ray and Ultraviolet Variability in NGC 5548
Nandra, K.; Clavel, J.; Reichert, G. A. +7 more
We present the result of a series of contemporaneous (within one day) hard X-ray (Ginga) and ultraviolet (IUE) observations of the Seyfert 1 galaxy NGC 5548. Nine of these observations were carried out over a period of 51 days in 1990 May-July, and two in 1989. An additional simultaneous IUE-EXOSAT observation obtained on 1984 May 21 is also analy…
The Abundance of Boron in Three Halo Stars
Lambert, David L.; Lemke, Michael; Duncan, Douglas K.
B abundances for three halo stars: HD 140283, HD 19445, and HD 201891 are presented. Using recent determinations of the Be abundance in HD 140283, B/Be of 10 +5/-4 is found for this star, and similar ratios are inferred for HD 19445 and HD 201891. This ratio is equal to the minimum value of 10 expected from a synthesis of B and Be by high-energy c…
Ultraviolet Observations of the Gas Phase Abundances in the Diffuse Clouds toward zeta Ophiuchi at 3.5 Kilometers per Second Resolution
Savage, Blair D.; Sofia, Ulysses J.; Cardelli, Jason A.
Goddard High Resolution Spectrograph echelle mode measurements at 3.5 km/s resolution are presented for interstellar absorption produced by C II, O I, Mg I, Mg II, Al III, P II, Cr II, Mn II, Fe II, Ni II, Cu II, Zn II, Ga II, Ge II, and Kr I. The absorption line measurements are converted into representations of apparent column density per unit v…