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Determinations of the interstellar reddening toward Wolf-Rayet stars of the nitrogen sequence from observed UBV color indices.
Schmutz, W.; Vacca, W. D.
We demonstrate that continuum discontinuities, or "jumps", are present in the spectra of some Wolf-Rayet stars and that current models of Wolf-Rayet stars predict such jumps and provide good fits to the observed continua. Using a relation between the size of the He II (n = 4) jump at 3645 A and the intrinsic (b - v)_0_ color found from the model a…
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, …
The Discovery of an X-Ray Burst and a Study of Aperiodic Variability from SMC X-1
Stella, L.; White, N. E.; Angelini, L.
The aperiodic X-ray variability of the 0.7 s X-ray pulsar SMC X-1 is investigated using five EXOSAT observations made in 1984 October and November. During the first observation an X-ray burst was observed, where the source count rate increased by a factor of ~ 3 in less than ~ 0.7 s, and then erratically decayed to the preburst level over ~ 80 s. …
The Ionization Structure of Planetary Nebulae. X. NGC 2392
Barker, Timothy
Spectrophotometric observations of emission-line intensities over the spectral range 1400 to 7200 A were made in six positions in the planetary nebula NGC 2392. Standard equations used to correct for the existence of elements in other than the optically observable ionization stages give consistent results for the different positions that are in ex…
On the X-Ray--emitting Boundary Layer of the Dwarf Nova VW Hydri
Mauche, Christopher W.; Polidan, Ronald S.; Wade, Richard A. +2 more
The temperature and luminosity of the boundary layer of VW Hyi are constrained to kT(BL) of about 10.5 eV, and L(BL) of about 6 x 10 to the 32nd (d/65 pc)squared ergs/sec. This is based on Voyager far- and extreme-ultraviolet spectrophotometry and a measurement of the column density of neutral hydrogen, combined with Exosat LE filter observations.…
The X-Ray Properties of GX 301-2 (4U 1223-62)
Haberl, F.
The X-ray luminosity of the X-ray binary pulsar GX 301 - 2 exhibits a strong maximum near periastron passage of the neutron star, or phase 0, but with the peak 0.05 in phase before. During the interval between phase 0.9 and 0.25, during periods when the absorption was high, the X-ray spectra indicate a strong low-energy excess that may be modeled …
An IUE and optical study of interstellar gas towards stars within the Cygnus OB1 and OB3 associations.
Smith, L. J.; St. -Louis, N.
The interstellar absorption lines formed towards 13 members of the Cyg OB1 and OB3 associations were examined in detail using IUE and optical spectra. Low (0 to +17 km/s), intermediate (-24 km/s), and high (-40 to -70 km/s) velocity components were detected toward most of the stars. It is found that the main component of the highly ionized species…
First Results from the Faint Object Camera: High-Resolution Observations of the Central Object R136 in the 30 Doradus Nebula
Boksenberg, A.; Barbieri, C.; Weigelt, G. +16 more
R 136 is the luminous central object of the giant H II region 30 Doradus in the Large Magellanic Cloud. We report on the first high- resolution observations of RI 36 with the Faint Object Camera on board the Hubble Space Telescope. The physical nature of the brightest component R136a has been a matter of some controversy over the last few years. T…