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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…
Disk-Overflow Accretion in GK Persei?
Hellier, Coel; Livio, Mario
We reanalyze the 1983 European X-ray Observatory Satellite (EXOSAT) observations of GK Per during an outburst to investigate the approximately 5000 s quasiperiodic modulation. We find that the spectral behavior is reminiscent of dipping low-mass X-ray binaries and note that the time scale is characteristic of the radius where an accretion stream o…
Ultraviolet Light Curves of beta Lyrae: Comparison of OAO A-2, IUE, and Voyager Observations
Kondo, Yoji; Polidan, Ronald S.; Eaton, Joel A. +3 more
The six-band ultraviolet light curves of beta Lyrae obtained with the Orbiting Astronomical Observatory (OAO) A-2 in 1970 exhibited a very unusual behavior. The secondary minimum deepened at shorter wavelength, indicating that one was not observing light variations caused primarily by the eclipses of two stars having a roughly Planckian energy dis…
Emission Lines in the Long-Period Cepheid L Carinae
Bohm-Vitense, Erika; Love, Stanley G.
For the Cepheid l Carinae, with a pulsation period of 35.5 days, we have studied the emission-line fluxes as a function of pulsational phase in order to find out whether we see chromospheric and transition-layer emission due to an outward-moving shock. All emission lines show a steep increase in flux shortly before maximum light, suggestive of a s…
The Hubble Space Telescope Extragalactic Distance Scale Key Project. II. Photometry of WFC Images of M81
Illingworth, Garth D.; Madore, Barry F.; Freedman, Wendy L. +11 more
The Extragalactic Distance Scale (H_0_) Key Project for Hubble Space Telescope (HST) aims to employ the Cepheid period-luminosity (P-L) relation to measure galaxy distances out as far as the Virgo Cluster. The vital steps in this program are (1) to obtain precise photometry of stellar images from the Wide Field Camera (WFC) exposures of selected g…
IUE Spectra and Optical Imaging of the Oxygen-rich Supernova Remnant N132D
Blair, William P.; Raymond, John C.; Long, Knox S.
We present new optical Charge Coupled Devices (CCD) interference filter imagery and International Ultraviolet Explorer (IUE) spectroscopy for the oxygen-rich supernova remnant N132D in the Large Magellanic Cloud. The optical images show a wealth of structure, and comparison with an archival Einstein High Resolution Imager (HRI) X-ray image shows t…