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Radio Emission from Galactic Wolf-Rayet Stars and the Structure of Wolf-Rayet Winds
Churchwell, E.; Abbott, D. C.; Torres, A. V. +1 more
The authors have observed 23 Wolf-Rayet stars with the VLA at 6 cm and reobserved four stars at both 2 and 6 cm. When combined with previous data, these observations form an essentially complete sample of 40 W-R stars within a distance of 3 kpc and north of declination -47°. Available measurements of optical emission lines are used to estimate the…
Active Extragalactic Sources: Nearly Simultaneous Observations from 20 Centimeters to 1400 Angstrom
Landau, Robert; Golisch, Bill; Jones, Terry J. +15 more
IRAS, IUE, and ground-based optical, NIR, mm and submm, and radio observations obtained mainly on Apr. 9-23, 1983, are reported for 19 active extragalactic sources and eight control sources. The overall spectra of the compact active sources are shown to be well represented by continuous-curvature functions such as parabolas. The spectra are found …
The Discovery of 3.8 Hour Periodic Intensity Dips and Eclipses from the Transient Low-Mass X-Ray Binary EXO 0748-676
Parmar, A. N.; White, N. E.; Giommi, P. +1 more
Using the EXOSAT Observatory the authors have discovered a new transient X-ray burst source EXO 0748-676 that shows 8.3 minute duration X-ray eclipses that recur with a period of 3.82 hr. If the companion star is on the main sequence, the eclipse duration gives a companion mass of 0.45 M_sun; and a system inclination of 75°. Irregular intensity di…
IUE Spectra and a Resulting Model of Seyfert 2 Galaxies
Ferland, G. J.; Osterbrock, D. E.
Nearly simultaneous optical and ultraviolet observations of several Seyfert 2 galaxies are presented. A mean optical to ultraviolet emission line spectrum for Seyfert 2 galaxies is determined, and these intensities are compared with predictions of photoionization models. The UV to X-ray nonthermal continuum which ionizes this gas is examined. The …
X-Ray and Optical Observations of the Ultrashort Period Dwarf Nova SW Ursae Majoris: A Likely New DQ Herculis Star
Szkody, P.; Shafter, A. W.; Thorstensen, J. R.
Optical photometric and spectroscopic and X-ray observations of the dwarf nova SW UMa are presented. Moderate resolution spectroscopic data have established an orbital period of 81.8 min and have revealed that the Balmer emission lines have a multiple structure. A narrow component, similar to the s-wave component which is sometimes seen in catacly…
X-Ray Sources in Regions of Star Formation. I. The Naked T Tauri Stars
Walter, F. M.
Einstein X-ray observations of regions of active star formation in Taurus, Ophiuchus, and Corona Australis show a greatly enhanced surface density of stellar X-ray sources over that seen in other parts of the sky. Many of the X-ray sources are identified with low-mass, pre-main-sequence stars which are not classical T Tauri stars. The X-ray, photo…
Ultraviolet and Visual Wavelength Spectroscopy of Gas around Eta Carinae
Davidson, K.; Gull, T. R.; Dufour, R. J. +1 more
Observational results of η Carinae are reported, especially spectroscopy of the outer 'S condensation' supplemented by data on the homunculus and its core. Theoretical calculations of atmosphere/wind models and of the shock-heated S condensation are needed for a proper analysis of the data, but some simplified results are discussed. The helium abu…
Cometary Grain Scattering versus Wavelength, or, ``What Color Is Comet Dust?''
Jewitt, David; Meech, Karen J.
Optical and near-infrared observations of comets are combined in a systematic study of the wavelength dependence of the scattering from cometary grains. The normalized rate of change of the reflectivity of cometary grains with respect to the wavelength of observations decreases as the wavelength increases. The observed wavelength dependence of the…
New Results on the X-Ray Emission and Its Correlation with the Ultraviolet in NGC 4151
Piro, L.; Perola, G. C.; Altamore, A. +8 more
Results from observations of the Seyfert galaxy NGC 4151 obtained with Exosat (0.1-25 keV) and IUE (1200-3000 A) during November 1983, and between December 1984 and January 1985, are presented. The stability of the flux during large-scale variations in the UV and X-ray regions suggests that the soft X-ray excess noted by Holt et al. (1980) represe…
Spectroscopic Studies of Wolf-Rayet Stars. III. The WC Subclass
Conti, P. S.; Massey, P.; Torres, A. V.
Wolf-Rayet (W-R) stars, which are the descendants of massive O-type stars, can be subdivided into three groups depending on their spectral appearance. These groups include the nitrogen class (WN), the carbon class (WC), and the oxygen class (WO). The present paper is concerned with the WC stars. The assignment of WC subtypes has been based on visu…