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First Results from the Goddard High-Resolution Spectrograph: The Chromosphere of alpha Tauri
Ebbets, Dennis C.; Brown, Alexander; Walter, Frederick M. +5 more
The K5 III star Alpha Tau was observed with the Goddard High Resolution Spectrograph on November 27, 1990 as part of the Science Assessment Program for the HST. The spectra show intersystem and permitted chromospheric emission lines of semiforbidden C II and Si II, Fe II, Fe I, Ni II, and Co II. Resolved profiles of the semiforbidden C II lines in…
A Study of the Ultraviolet Evolution of U Geminorum between Outbursts
Szkody, Paula; Sion, Edward M.; Kiplinger, Alan L.
This paper examines the ultraviolet evolution of the dwarf nova U Gem from one outburst to the next. A series of seven sets of IUE observations that monitor the quiescent period of 22-103 days after outbursts is presented. An eighth set of observations obtained 75 days after the second outburst is included for comparison. In agreement with earlier…
PW Vulpeculae: A Nova with Nearly Solar Abundances
Williams, Robert E.; Truran, James W.; Ferland, Gary J. +6 more
Optical spectrophotometry of PW Vulpeculae is combined with ultraviolet data to estimate electron temperatures, densities, and abundances in the ejecta of this slow classical nova. The reddening, the distance, and the evolution of the ultraviolet spectrum are discussed. Abundances are nearly solar, with the exception of nitrogen, which is substant…
The Local Interstellar Medium toward the Center of Loop I
Vladilo, Giovanni; Centurion, Miriam
The present study of the local insterstellar medium toward the center of Loop I analyzes optical and UV spectra of nearby stars within the l = 310-330 deg, b = 15-25 deg area. The analysis of the UV spectra reveals a sudden gas-column density increase as a function of distance from 10 to the 18th to 10 to the 20th/sq cm, suggesting the presence of…
Faint Object Spectrograph Spectroscopy of Resolved Structure in the Nucleus of NGC 1068
Ford, H. C.; Kriss, G. A.; Armus, L. +7 more
We report the results of FOS spectroscopy of the continuum peak of NGC 1068 in the wavelength range 2200-7000 A. Detailed analysis reveals the emission lines to be complex in shape and to consist of a number of different velocity components. Both the Balmer lines and the strong forbidden lines have a contribution from a component with full width a…
The Orbital Ephemeris and Eclipse Transitions of the Low-Mass X-Ray Binary EXO 0748-676
Parmar, A. N.; Verbunt, F.; Corbet, R. H. D. +1 more
Using the eclipses as fiducial markers, an updated ephemeris for EXO 0748 - 676 is derived and evidence is found that between February 1985 and March 1989 the 3.82-h orbital period of EXO 0748 - 676 decreased with a time scale of -5 x 10 to the 6th yr. The sense of this change is the same as that predicted by simple models for the evolution of low…
Multiwavelength Observations of Nova LMC 1990 Number 2: The First Extragalactic Recurrent Nova
Williams, R. E.; Shore, Steven N.; Sonneborn, George +4 more
We present IUE and optical observations of Nova LMC 1990 Number 2, the first recurrent nova to be observed outside the Milky Way. The earlier optical outburst of the nova was observed in 1968, when it reached a maximum of about V = 10.9. IUE spectra were obtained between 1990 February 16 and March 26, with 8 hr resolution during the first day of o…
A Spectroscopic Search for Colliding Stellar Winds in O-Type Close Binary Systems. I. AO Cassiopeiae
Wiggs, Michael S.; Gies, Douglas R.
AO Cas, a short-period, double-lined spectroscopic binary, is studied as part of a search for spectroscopic evidence of colliding stellar winds in binary systems of O-type stars. High S/N ratio spectra of the H-alpha and He I 6678-A line profiles are presented, and their orbital-phase-related variations are examined in order to derive the location…
Ionization Fronts and Shocked Flows: The Structure of the Orion Nebula at 0 -0.5pt.1
O'Dell, C. R.; Lauer, Tod R.; Faber, S. M. +15 more
Initial results are presented from images of the Orion Nebula obtained with the HST Wide-Field Camera with a resolution of better than about 10 to the 15th cm. The morphology of the forbidden S II emission is markedly different from that seen in H-beta and forbidden O II. The forbidden S II is dominated by filamentary features with widths between …
First Results from the Faint Object Camera: Observations of PKS 0521-36
Boksenberg, A.; Barbieri, C.; Weigelt, G. +16 more
The Faint Object Camera on the Hubble Space Telescope was used to observe the radio galaxy PKS 0521 - 36 which hosts a prominent radio jet. Images of the jet show spatial structure comparable to VLA data and significantly better than optical ground-based observations. The jet structure is resolved at FOC resolution. In addition to the radio knot, …