Search Publications
BE UMa (PG 1155+492) : a unique cataclysmic-variable-like object.
Spinrad, H.; Green, R. F.; Liebert, J. +2 more
The variable spectrum of BE Ursae Majoris, which is similar to that of the cataclysmic variables (CVs), shows (1) an emission-line spectrum with the high-excitation CN 4650 A blend as the strongest optical feature, weaker H and He lines, and a strong Balmer jump, and (2) an absorption spectrum dominated by He. Although the object shows no evidence…
The ultraviolet spectrum of the magnetic degenerate star GD 229.
Green, R. F.; Liebert, J.
The ultraviolet spectrum obtained with the IUE satellite of the magnetic degenerate white dwarf star GD 229 is presented. The ultraviolet energy distribution measured by the short- and long-wavelength cameras covering the range 1170-3200 A, when combined with optical data, indicates a best fit blackbody temperature of 16,000 K, which is significan…
The ultraviolet interstellar extinction curve in the Pleiades.
Bohlin, R. C.; Witt, A. N.; Stecher, T. P.
The wavelength dependence of ultraviolet extinction in the Pleiades dust clouds has been determined from IUE observations of HD 23512, the brightest heavily reddened member of the Pleiades cluster. There is evidence for an anomalously weak absorption bump at 2200 A, followed by an extinction rise in the far ultraviolet with an essentially normal s…
3C273 - a Review of Recent Results
Ulrich, M. -H.
3C 273 is the most extensively studied quasar both from the ground and from space. Recent satellite observations have given important information on the overall electromagnetic spectrum of 3C 273 in the γ-ray, X-ray, and UV ranges. The most salient results are: (i) the energy per decade of frequency emitted by 3C 273 is nearly constant between 600…
Quasi-simultaneous observations of BL Lac object MRK 501 in X-ray, UV, visible, IR, and radio frequencies.
Kondo, Y.; Yee, H. K. C.; Worrall, D. M. +8 more
Observations in the X-ray, UV, visible, IR and radio regions of the BL Lac object Mrk 501 made over the course of two months are reported. The measurements were made with the A2 experiment on HEAO 1 (X-ray), the SWP and LWR cameras on IUE (UV), the 5-m Hale telescope (visible), the 2.5-m telescope at Mount Wilson (IR), the NRAO 92-m radio telescop…
The dwarf nova Z Cha. II. Spectroscopy.
Rayne, M. W.; Whelan, J. A. J.
Spectroscopic observations are presented of Z Cha in quiescence. The data include moderate spectral resolution scans over the greater part of an orbit and with high time resolution through eclipse. Also discussed are various lower resolution spectra and UV and optical spectrophotometry. The spectrum is found to be dominated by broad double peaked …
The variable shell star HR 5999 : V. The spectral energy distribution.
Liseau, R.; Wamsteker, W.; The, P. S. +10 more
From April to August 1978 an international campaign was organized to observe the variable shell star HR 5999 with different techniques. A study of part of the collected material yields the following results. The visual light variation follows the general pattern as found at earlier observations ; the star stays usually long around maximum brightne…
The optical and ultraviolet spectra of the high excitation planetary nebula, CD -23 12238 = ME 2-1.
Czyzak, S. J.; Keyes, C. D.; Aller, L. H.
Planetary nebula are now recognized as a penultimate stage in the evolution of many stars. Me 2-1 offers advantages meriting a detailed analysis. A description is presented of measurements regarding this object which have been conducted with a photoelectric scanner and a 3 m telescope Cassegrain image tube scanner. The chemical composition of Me 2…
Ultraviolet spectra of planetary nebulae. IV. The CIII 2297 dielectronic recombination line and dust absorption in the CIV 1549 resonance doublet.
Harrington, J. P.; Lutz, J. H.; Seaton, M. J.
Calculations by Storey confirm, as suggested in Paper I of the present series, that dielectronic recombination via low-lying auto-ionizing states is important for the calculation of the ionization equilibria of carbon ions. These processes also produce various spectrum lines, of which one is C III 2p2 1D → 2s 2p 1P…
The ultraviolet spectrum of the active elliptical galaxy NGC 1052.
Boksenberg, A.; Penston, M. V.; Snijders, M. A. J. +1 more
Low resolution IUE observations of NGC 1052 in both the long and the short wavelength regions are reported along with optical multi-aperture photometry. It is found that the ultraviolet energy distribution of NGC 1052 is similar to that of other normal galaxies observed with IUE, having a large excess at short wavelengths above the extrapolation o…