Search Publications
Narrowband HST Imagery of the Young Planetary Nebula Henize 1357
Bobrowsky, M.
We present Hubble Space Telescope (HST) Planetary Camera observations showing the first optically resolved images of the planetary nebula Henize 1357 . The small size of this object has heretofore precluded optical investigations of its morphology. In H-beta, He 3-1357 appears to have an equatorial ring of enhanced density tilted approximately 56 …
Low-Velocity Variability in the Stellar Wind of HD 152408 (O8: Iafpe)
Fullerton, A. W.; Prinja, Raman K.
We describe high-quality, spectroscopic time series observations of variability at low velocities in the stellar wind of the extreme O-supergiant HD 152408. These observations were obtained during a monitoring campaign coordinated between Australia and Chile in 1992 July. Systematic variability on hourly time scales is particularly apparent in the…
Intersystem Transitions of Interstellar Carbon Monoxide toward zeta Ophiuchi
Federman, S. R.; Lambert, David L.; Cardelli, Jason A. +2 more
Absorption from seven intersystem (triplet-singlet) transitions of interstellar (12)CO were detected in ultraviolet spectra of zeta Oph. The observed equivalent widths are approximately consistent with the transitions' predicted f-values and the (12) CO column density derived from the weakest of the observed A-X bands. These unsaturated intersyste…
Interstellar Gas and Dust in the Young Cluster IC 348
Snow, Theodore P.; Hanson, Margaret Murray; Seab, Gregory C. +1 more
We have completed a multiband absorption- and emission-line study of a star embedded in the young cluster IC 348, to determine the environmental effect of star formation on the interstellar medium (ISM) local to the region. The hottest and youngest star in IC 348 is BD +31 deg 643, a B5 V star which samples the inner bright nebular region. The nea…
An Ultraviolet and Visible Spectroscopic Study of a Pulsational Cycle of RY Sagittarii
Cottrell, P. L.; Lawson, W. A.; Clayton, Geoffrey C. +3 more
High-dispersion visible and ultraviolet spectra and UBVRI photometry, covering a complete pulsation of the R Coronae Borealis star RY Sgr, have been obtained. The UV spectra were the first high-dispersion data ever obtained for the star. Together these observations comprise the most complete data set covering an RCB star pulsation cycle. The cycle…
X-Ray Spectral Study of Two X-Ray Binaries: 4U 1957+11 and 2S 1543-624
Kraft, Ralph P.; Apparao, Krishna M. V.; Singh, Kulinder P.
The X-ray observations of two binary systems, 4U 1957+11 and 2S 1543-624, by the High Eccentric Lunar Occultation Satellite (EXOSAT) satellite are analyzed. The continuum spectra are best fitted by a superposition of a blackbody spectrum (kT approximately = 1 keV) and emission from a Comptonized region, consistent with the spectra of low-mass X-ra…
AL iii, SI iv, and C IV Absorption toward zeta Ophiuchi: Evidence for Photoionized and Collisionally Ionized Gas
Jenkins, Edward B.; Sembach, Kenneth R.; Savage, Blair D.
We present Goddard High-Resolution Spectrograph observations at 3.5 km/s resolution and signal-to-noise ratios of 30 to 60 for the Al III, Si IV, and N V absorption lines in the far-ultraviolet spectrum of the O9.5 V star zeat Ophiuchi. The measurement reveal three types of highly ionized gas along the 140 pc line of sight. (1) Narrow components o…
Spectrum of IC 2149 and Its Central Star
Feibelman, Walter A.; Hyung, Siek; Aller, Lawrence H.
Although the asymmetric optical image of IC 2149 does not fall into any standard morphologies (Balick et al. 1993), the overall shape and its radio frequency image show a bilateral symmetry. The central star of spectral class O7.5 is a remarkable object with a rich spectrum showing many Fe ions. We discuss this spectrum in detail. The nebula has b…
Ellipticals with Kinematically Distinct Cores: HST Imaging of the Nuclear Structure of IC 1459
Franx, Marijn; Illingworth, Garth D.; Forbes, Duncan A.
The elliptical galaxy IC 1459 has one of the strongest counter- rotating core components of any observed elliptical. Here we present HST Planetary Camera images of the center of IC 1459. Before deconvolution, our V band images reveal a bright point source at the galaxy nucleus, and dust near the nucleus. After removal of the central point source, …
The Multifrequency Spectral Evolution of Blazar 3C 345 during the 1991 Outburst
Crenshaw, D. M.; Kazanas, D.; Miller, H. R. +21 more
The blazar 3C 345 underwent a 2.5 mag optical outburst between 1990 November and 1991 May. We have obtained 10 nearly simultaneous multifrequency spectra during the course of the outburst in order to study the multifrequency spectral variations of 3C 345 as a function of time. Although our observations were not sampled frequently enough to complet…