Search Publications
Observations of the Bowen Fluorescent Mechanism in Planetary Nebulae
Aller, L. H.; Likkel, L.
Measurements of Bowen fluoresecent lines in 17 planetary nebulae are presented and the relative line strength is composed with theory. There is generally good agreement with the line intensities expected by Saraph and Seaton (1980). The largest deviation from theory is in the O III I(3429A/I3444A) ratio, which is consistently lower than predicted.…
Detection of Scattering in the 2175 Angstrom Interstellar Band
Bohlin, R. C.; Witt, A. N.; Stecher, T. P.
Spectrophotometric observations of two reflection nebulae and their illuminating stars obtained with the International Ultraviolet Explorer Satellite have provided the first evidence for the presence of a scattering contribution to the 2175 A interstellar extinction band. Lower than normal far-UV extinction for the stars embedded in the nebulae in…
Variability of Lyman-Alpha and the Ultraviolet Continuum of 3C 446
Huggins, P. J.; Kinney, A. L.; Bregman, J. N. +1 more
IUE observations have been conducted over the 1230-3175 A range for the violently variable quasar 3C 446, beginning in June 1980, at intervals of 1.2, 2.2, 0.5, and 0.4 yr. Strong absorption of the continuum was found below 1830 A, probably corresponding to a Lyman edge at z of 1.00 + or - 0.01. The absence of Mg II 2798 A absorption implies that …
Multifrequency Observations of the Blazar PKS 0537-441 in a Moderately Active State
Maraschi, L.; Tanzi, E. G.; Chiappetti, L. +6 more
PKS 0537-441 was observed during an active state in February 1985 at infrared, optical, UV, and X-ray frequencies. Comparison with earlier measurements indicates that the source brightened by a factor of approximately 2 in all bands. This suggests that the same spatial region may be responsible for the emission in the whole spectral range observed.
Dust in the Emission-Line Gas of the Seyfert 2 Galaxy Markarian 3
Harrington, J. P.; Kraemer, S. B.
The results of photoionization models of the emission-line gas of the type 2 Seyfert galaxy Mrk 3 are presented. The models include cosmic dust with spectral properties similar to that found in the Galaxy. The effect of dust within the gas on the transfer of line radiation, particularly the UV resonance lines, and the contribution of the hot dust …
More Low-Redshift Broad Absorption Line QSOs
Turnshek, David A.; Grillmair, Carl J.
The discovery of two new broad absorption line (BAL) QSOs with emission redshifts of 1.024 and 0.129 is reported. The discovery of the two new low-redshift BAL QSOs strengthens the evidence that the fraction of QSOs with BALs at low redshifts is similar to the 3-10-percent fraction found at higher redshifts. In particular, the analysis suggests th…
A Survey of Interstellar Sulfur Abundance and Implications for P II Oscillator Strengths
Harris, A. W.; Mas Hesse, J. M.
A study of interstellar gas-phase S abundance is presented which is based mainly on abundances for 39 sight lines newly derived from recently published Copernicus UV absorption-line measurements and archival IUE data. A trend of increasing depletion with increasing mean H volume density n-bar(H) is evident which is similar to that already establis…
Near-Ultraviolet Spectroscopy of Seyfert Nuclei: Reddening and Bowen Fluorescence
Malkan, Matthew A.
Spectra with high signal-to-noise ratios extending down to the atmospheric ultraviolet cut-off have been obtained for 11 Seyfert nuclei with narrow emission lines. In all objects the He II lines at 3204 A and 4686 A were measured simultaneously. Their ratio gives an estimate of reddening accurate to 0.14 mag in E(B-V). The redshifts of nine of the…
Neutral Oxygen and Sulfur Densities in the Io Torus
Skinner, T. E.; Durrance, S. T.
Ultraviolet spectra (1150-1750 A) of the Io torus, obtained using a rocket-borne telescope and spectrometer in May 1981, show emissions of neutral sulfur and neutral oxygen, as well as ionic emissions of S II, S III, and S IV. The emissions are observed almost 180 deg from the location of the satellite Io and imply the existence of an extended neu…
EXOSAT Results on V426 Ophiuchi: Indications of a DQ Herculis System
Szkody, P.
EXOSAT LE and ME data reveal a sinusoidal l hr modulation during the 6 hr binary orbit of the cataclysmic variable V426 Oph. The amplitude and shape of this modulation, the X-ray fluxes and spectrum, as well as the time scales involved argue for a DQ Her interpretation. In this case, the white dwarf in V426 Oph has the longest rotation period amon…