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The Time Variability of the Ultraviolet Continuum and Lyman-Alpha in 3C 273
Wamsteker, W.; Ulrich, M. -H.; Courvoisier, T. J. -L.
This article presents the light curve of the ultraviolet (UV) continuum flux and of the Lyα emission line of 3C 273 between 1978 and 1992.5. It also presents evidence for a quantitative difference between nearby Seyfert 1 and the quasar 3C 273 regarding the response of the emission lines to UV continuum flux variations. In contrast to what is obse…
HS 0209+0832 : a DAB white dawrf with a temperature fittinginto the DB gap.
Heber, U.; Jordan, S.; Koester, D. +1 more
The white dwarf H50209+0832 (B ≈13m.9), belonging to the sparse class of spectral type DAB, was discovered by follow-up spectroscopy of candidates selected from objective- prism plates of the Hamburg Schmidt sky survey. An analysis of the optical spectrum, clearly showing the He I λ4471 line besides the Balmer lines, yields a He/H ratio…
On the Chromospheric Structure of zeta Aurigae
Eaton, Joel A.
The chromospheric structure of Zeta Aur is analyzed on the basis of both optical and UV data. Column densities of matter along different lines of sight through the chromosphere are measured by using both Ly-alpha wings and many lines of ionized metals, and they agree to within the errors of measurement. The chromosphere is seen to extend at least …
A New Luminous Blue Variable: R143 in 30 Doradus
Parker, Joel Wm.; Clayton, Geoffrey C.; Conti, Peter S. +1 more
We have discovered that R143 in the Large Magellanic Cloud is a luminous blue variable (LBV), the first and perhaps the lone LBV in the central cluster of 30 Doradus, and only the sixth known LMC LBV. Photometric and spectroscopic observations over the past 40 yr indicate that during that time R143 moved redward (changing from an F5 to F8 supergia…
A General Bayesian Image Reconstruction Algorithm with Entropy Prior. Preliminary Application to HST Data
Nunez, Jorge; Llacer, Jorge
This paper describes a general Bayesian iterative algorithm with entropy prior for image reconstruction. It solves the cases of both pure Poisson data and Poisson data with Gaussian readout noise. The algorithm maintains positivity of the solution; it includes case-specific prior information (default map) and flatfield corrections; it removes back…
Cool stars : spectral energy distributions and model atmosphere fluxes.
Morossi, C.; Malagnini, M. L.; Kurucz, R. L. +2 more
The main results of a program of systematic comparison between observed and computed spectral energy distributions of late G and K type solar chemical composition stars are illustrated. We built the observed energy distributions of eleven representative stars, from the ultraviolet to the infrared, starting from lUE archive data, supplemented by ou…
IUE Short-Wavelength High-Dispersion Line List for the Symbiotic Nova RR Telescopii
Aufdenberg, Jason P.
An 820 minute and other long-exposure archival SWP IUE high-dispersion spectra of symbiotic star RR Tel have been combined to form a composite spectrum. In most of these spectra many lines are saturated, but weaker features appear above the continuum. Their wavelengths were measured from the composite spectrum and compared with the line list from …
Ultraviolet Spectroscopy of Herbig-Haro Objects: Spatial Structure, Spectroscopic Diagnostics, and Variability
Noriega-Crespo, A.; Boehm, K. -H.; Solf, J.
Using new long-exposure (two-shift) SWP IUE spectra of HH 2G, (HH 2H + HH 2A'), and HH 1F and archival spectra of (HH 2H + HH 2A') and of HH 1 we have obtained the following results:
1. For the first time we have determined a separate UV spectrum of the high-excitation condensation HH 2G. The spectrum shows similarity to that of HH 2R. Howeve…Detection of a White Dwarf Compensation to the Hyades Stars HD 27483
Boehm-Vitense, Erika
We observed with IUE a white dwarf (WD) companion to the Hyades F6 V binary stars HD 27483. This system is known to be a close binary of two nearly equal stars with an orbital period of 3.05 days. Our IUE observations revealed the presence of a third star, a white dwarf with an effective temperature of 23,000 +/- 1000 K and a mass of approximately…
The extended nebulosity in the radio galaxy 3C 227.
Walsh, J. R.; Prieto, M. A.; di Serego Alighieri, S. +1 more
3C 227 (z = 0.085) exhibits one of the more spectacular extended nebulosities to be found among active galaxies at moderate redshifts. The gas can be traced to radial distances of about 100 kpc (H_0_ = 50 km s^-1^ Mpc^-1^). The total [O III] 5007-A luminosity is 2.7 X 10^42^ erg s^-1^, of which at least 50 per cent is radiated from the extended re…