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Properties of the SN 1987A Circumstellar Ring and the Distance to the Large Magellanic Cloud: Erratum
Panagia, N.; Kirshner, R. P.; Macchetto, F. +2 more
Figures 2 and 3 of the Letter "Properties of the SN 1987A Circumstellar Ring and the Distance to the Large Magellanic Cloud," by N. Panagia, R. Gilmozzi, F. Macchetto, H.-M. Adorf, and R. P. Kirshner (ApJ, 380, L23 [1991]), contained some errors; i.e., Figure 2 had the wrong theoretical curve as a fit to the time evolution of the C III)λ1909 line …
Seyfert Galaxy Ultraviolet Emission-Line Intensities and Variability: A Self-consistent Photoionization Analysis Applied to Broad-Line--emitting Gas in NGC 3783
Koratkar, Anuradha P.; MacAlpine, Gordon M.
Both strong and weak ultraviolet emission lines in SeYfert 1 galaxies have been accurately measured from reextracted short-wavelength camera data in the IUE satellite data archives. Line ratios, equivalent widths, and trends as functions of continuum variability were used to constrain numerical modeling parameters in detailed photoionization analy…
The Analysis of Apparent Optical Depth Profiles for Interstellar Absorption Lines
Sembach, Kenneth R.; Savage, Blair D.
Attention is given to the apparent optical depth method, a procedure for analyzing interstellar absorption lines. Observed absorption-line profiles are converted into profiles of apparent optical depth, and apparent column density per unit velocity. By comparing the latter for a given interstellar species having two or more absorption lines which …
Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. I. an 8 Month Campaign of Monitoring NGC 5548 with IUE
Mazeh, T.; Glass, I. S.; Malkan, M. A. +54 more
We present emission-line and ultraviolet continuum observations of a type I Seyfert galaxy in which the time resolution is adequate for describing the character of variability. Using the IUE satellite, the nucleus of NGC 5548 was observed every 4 days for a period of 8 months. Its mean properties-continuum shape, line ratios-are not unusual for ty…
Ultraviolet Variability of NGC 5548: Dynamics of the Continuum Production Region and Geometry of the Broad-Line Region
Malkan, M. A.; Kriss, G. A.; Horne, Keith +3 more
We used the data obtained in the 1989-1990 IUE monitoring of NGC 5548 to derive a mean shape for the ionizing spectrum; mean line profiles; the continuum fluctuation power spectrum in three UV bands; cross-correlation functions relating these bands; cross-correlation functions relating fluctuations in eight emission lines to fluctuations in the UV…
Properties of the SN 1987A Circumstellar Ring and the Distance to the Large Magellanic Cloud
Panagia, N.; Kirshner, R. P.; Macchetto, F. +2 more
We have determined the distance to SN 1987A by comparing the angular size of its circumstellar ring, measured from an HST image obtained in a narrow [O III] 5007 A filter, with its absolute size derived from an analysis of the light curves of narrow UV lines (N V λ1240, N IV] λ1486, N III] λ1750, and C III] λ1909) measured with IUE. Our analysis c…
The Chromospheric Emission--Age Relation for Stars of the Lower Main Sequence and Its Implications for the Star Formation Rate
Soderblom, David R.; Duncan, Douglas K.; Johnson, Dean R. H.
An attempt is made to formulate the relationship between age and chromospheric emission (CE) in late-type dwarf stars. Evidence is reviewed that a deterministic relationship of this type actually exists, and that for stars of known age, either a power-law relation or a curve corresponding to a constant star formation rate fits equally well. Furthe…
The Great Flare of 1985 April 12 on AD Leonis
Hawley, Suzanne L.; Pettersen, Bjorn R.
A giant flare on the M dwarf star AD Leo is examined on the basis of photometric and spectroscopic observations covering the wavelength range 1200-1800 A. A flare energy budget over the entire optical and ultraviolet wavelength region is constructed as a function of time during the flare. The continuum radiation is shown to be the dominant source …
On Winds and X-Rays of O-Type Stars
Chlebowski, Tomasz; Garmany, Catharine D.
The dependence between stellar wind parameters and their X-ray fluxes is studied. Bolometric corrections are examined as a function of temperature, and a bolometric luminosity scale is proposed for the O-type stars. New mass-loss rates and terminal velocities of 40 well-known, bright single stars or binaries are measured, and the Lyman-alpha profi…
HST Imaging of the Inner 3 Arcseconds of NGC 1068 in the Light of [O iii] lambda 5007
Ford, H. C.; Armus, L.; Evans, I. N. +3 more
We have used the Planetary Camera on board the Hubble Space Telescope to obtain a high spatial resolution [O III] λ5007 image of the nucleus of NGC 1068. This image resolves the narrow-line region into several distinct clouds arranged in an apparently conical geometry. The individual emission-line regions appear to be resolved, with sizes ~0.1" -0…