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Hot Degenerates in the Montreal-Cambridge-Tololo Survey. II. Two New Hybrid White Dwarfs, MCT 0128-3846 and MCT 0453-2933, and the Nature of the DAB Stars
Kepler, S. O.; Fontaine, G.; Bergeron, P. +7 more
We report the discovery, in the course of a survey for high-latitude, ultraviolet-excess objects in the southern hemisphere, of two new hybrid DAB stars. Both objects exhibit a weak He I 4471 A line superposed onto the usual Balmer line spectrum. Analysis of the Balmer series with both homogeneous and stratified models show these stars to have spe…
X-Ray Continuum and Iron K Emission Line from the Radio Galaxy 3C 390.3
Elvis, M.; Fabbiano, G.; Hayashida, K. +8 more
X-ray properties of the radio galaxy 3C 390.3 were investigated using the EXOSAT and Ginga satellites. Long-term, large-amplitude X-ray intensity changes were detected over a period extending from 1984 through 1991, and high-quality X-ray spectra were obtained especially with Ginga. The X-ray continuum spectra were described with power-law model w…
First Hubble Space Telescope Observations of the Brightest Stars in the Virgo Galaxy M100 = NGC 4321
Casertano, Stefano; Ballester, Gilda E.; Kennicutt, Robert C. +24 more
As part of both the Early Release Observations from the Hubble Space Telescope and the Key Project on the Extragalactic Distance Scale, we have obtained multiwavelength BVR WFPC2 images for the face-on Virgo cluster spiral galaxy M100 = NGC 4321. We report here preliminary results from those observations, in the form of a color-magnitude diagram f…
Ultraviolet Spectra of HZ Herculis/Hercules X-1 from HST: Hot Gas during Total Eclipse of the Neutron Star
Anderson, Scott F.; Blair, William P.; Halpern, Jules P. +3 more
The Faint Object Spectrograph (FOS) aboard Hubble Space Telescope (HST) has been used in the UV to observe the prototypical X-ray pulsar Her X-1 and its companion HZ Her. Optical spectra were also obtained contemporaneously at the Kitt Peak National Observatory (KPNO) 2.1 m. The FOS spectra encompass the 1150-3300 A range near binary orbital phase…
Conditions in the Z = 0.692 Absorber toward 3CR 286
Cohen, Ross D.; Junkkarinen, Vesa T.; Beaver, E. A. +3 more
We present HST/FOS^1^ ultraviolet and ground-based optical spectra of the z = 0.692 21 cm absorption system in the QSO 3CR 286. The strength of the damped Lyα absorption implies an H I column density, N(H I)~2 x 10^21^ cm^-2^. We derive a high spin temperature for the H I gas, T_s_~> 10^3^ K, as has been found for other high-redshift 21 cm abso…
Gas Kinematics and Ionization along the Extended Sight Line to HD 116852
Sembach, Kenneth R.; Savage, Blair D.
We present Goddard High-Resolution Spectrograph intermediate observations of the interstellar medium toward HD 116852, a low halo star at a distance of 4.8 kpc (z = -1.3 kpc) in the direction l = 304. deg 9, b = 16.deg 1. The small science aperture observations have signal-to-noise ratios ranging from 30 to 90 and resolutions of 11 to 18 km/s (FWH…
N III Intercombination Lines in the IUE Spectra of Gaseous Nebulae
Feibelman, W. A.; Dufton, P. L.; Keenan, F. P. +3 more
Theoretical N III electron density-sensitive emission-line ratios involving intercombination transitions, derived using recent calculations of electron impact excitation rates and oscillator strengths, are presented for R1 = I(1754.0 Å)/I(1749.7 Å), R2 = I(1752.2 Å)/I(1749.7 Å), R3 = I(1748.6 Å)/I(1749.7 Å), and R<…
The Chromospheric Structure of the Cool Giant Star G Herculis
Johnson, Hollis R.; Luttermoser, Donald G.; Eaton, Joel
Non-Local Thermodynamic Equilibrium (LTE) calculations of semiempirical chromospheric models are presented for 30 g Her (M6 III). This star is one of the coolest (Teff = 3250 K) SRb (semiregular) variable stars and has a mass perhaps as great as 4 solar mass. Chromospheric features we have observed in its spectrum include Mg II h and k;…
A Statistical Equilibrium Analysis of Interstellar CO toward zeta Ophiuchi as Recorded by the Goddard High Resolution Spectrograph
Smith, Andrew M.; Bruhweiler, Frederick C.; Lyu, Cheng-Hsuan
High-resolution and high signal-to-noise ratio echelle observations made by the Goddard High Resolution Spectrograph (GHRS), aboard the Hubble Space Telescope, of molecular (12)C(16)O and (13)C(16)O in the absorbing gas toward zeta Oph are reported. A statistical equilibrium model, incorporating a different way of dealing with the radiation field …
Comparison of New Experimental and Astrophysical f-Values for Some RU II Lines, Observed in HST Spectra of chi LUPI
Wahlgren, Glenn M.; Leckrone, David S.; Johansson, Sveneric G. +6 more
We report an experimental absolute oscillator strengths for 18 UV lines of Ru II, obtained by combining laser-induced flourescence measurements of radiative lifetimes and branching fractions from line intensities in a calibrated Fourier-transform spectrum Hubble Space Telescope/Goddard High Resolution Spectrograph (HST/GHRS) observations of the sp…