Search Publications
Ultraviolet Polarimetry and Spectroscopy of the BL Lacertae Object PKS 2155-304
Anderson, Scott F.; Miller, Bryan W.; Smith, Paul S. +3 more
We present ultraviolet spectropolarimetry of the BL Lac object 2155 - 304. These observations were made using the Hubble Space Telescope and the Faint Object Spectrograph and, represent the first opportunity to study the wavelength dependence of the UV (1360-3300 A) linear polarization in a BL Lac object. Nearly simultaneous ground-based optical p…
The Luminosity Dependence of the X-Ray Spectrum of the Transient 42 Second Pulsar EXO 2030+375
Parmar, A. N.; White, N. E.; Reynolds, A. P.
We report on the evolution in the X-ray spectrum of the transient X-ray pulsar EXO 2030 + 375 during part of an outburst in 1985 May-August. The overall continuum spectral shape is similar to that of other accreting pulsars and can be represented by a power-law spectrum modified at low energies by significant absorption and at high energies either…
Implications of the Soft X-Ray versus Hard X-Ray Temporal Relationship in Solar Flares
Mariska, John T.; Li, Peng; Emslie, A. Gordon
We have calculated the time profiles of spatially integrated hard X-ray (30-500 keV) and soft X-ray (1-8 Å) emission in both thick-target electron-heated models, and bulk heated thermal models, of the impulsive phase of solar flares. For the thermal model, we find a serious difficulty: the time profiles of the 30-500 keV hard X-ray emission do not…
The Center of Gravity and Density Profile of 47 Tucanae
Calzetti, D.; Paresce, F.; de Marchi, G. +1 more
From the analysis of HST-FOC images of the globular cluster 47 Tuc, we have determined the position of the center of gravity to be about 6 arcsec away from the luminosity center. The luminosity center is mainly determined by an 'asymmetry' in the luminosity distribution of the stars brighter than m(342) about 16.5. The density profile from the dyn…
An X-Ray Excited Wind in Centaurus X-3
Stevens, Ian R.; Day, C. S. R.
We propose a new interpretation of the behavior of the notable X-ray binary source Centaurus X-3. Based on both theoretical and observational arguments (using EXOSAT data), we suggest that an X-ray excited wind emanating from the O star is present in this system. Further, we suggest that this wind is responsible for the mass transfer in the system…
Variable C IV Absorption in the Seyfert Galaxy NGC 5548: A Connection to Broad Absorption Line Quasi-stellar Objects?
Shull, J. Michael; Sachs, Elise R.
This is the second in a series of papers examining variable absorption components in the broad emission lines of Seyfert 1 galaxies. In an IUE survey of a complete sample of CfA Seyfert galaxies, we find that at least 12% and perhaps as many as 27% of the objects show evidence of intrinsic absorption in C IV 1549. In this paper, we use data from a…
Faint Object Spectrograph Spectra of the Broad Fe II Absorption Lines in the Remnant of SN 1006
Sarazin, Craig L.; Crenshaw, D. Michael; Fesen, Robert A. +2 more
Ultraviolet spectra of a hot subdwarf star located behind the remnant of SN 1006 have been obtained with the Faint Object Spectrograph on the Hubble Space Telescope. The FOS UV spectra show strong and extremely broad Fe II λ2343, λ2374, λ2382, λ2586, and λ2599 lines in absorption from the supernova remnant, confirming an earlier detection with the…
Chromospheric Heating by Acoustic Shocks: A Confrontation of GHRS Observations of alpha Tauri (K5 III) with AB Initio Calculations
Judge, P. G.; Cuntz, M.
We compare ab initio calculations of semiforbidden C II line profiles near 2325 A with recently published observations of the inactive red giant Alpha Tau (K5 III) obtained using the GHRS on board the Hubble Space Telescope. Our one-dimensional, time-dependent calculations assume that the chromosphere is heated by stochastic acoustic shocks genera…
Companions to Bright S and MS Stars: Technetium Deficiency and Binarity
Johnson, Hollis R.; Ake, Thomas B.; Ameen, Mudhaffer M.
To test the popular hypothesis that technetium-deficient stars of spectral types S and MS are mass-transfer binaries, we have searched for ultraviolet light from the putative hot secondaries in spectra taken with the SWP spectrograph of IUE. Although most S and MS stars are apparently thermally pulsing AGB (asymptotic giant branch) stars whose sur…
High-Resolution Ultraviolet Observations of the Interstellar Diffuse Clouds toward MU Columbae
Savage, Blair D.; Sofia, Ulysses J.; Cardelli, Jason A.
Data obtained from the Goddard High Resolution spectrograph (GHRS) are used to study differences in gas-phase abundances of ions occurring in the diffuse neutral clouds toward mu Col. The sight-line characteristics determined in previous studies are reviewed and results for the cloud velocities, absorption equivalent widths, ion column densities, …