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The Disappearing Broad Absorption Lines and Variable Emission Lines in NGC 3516
Robinson, Andrew; Horne, Keith; Goad, Michael R. +17 more
The Seyfert 1 galaxy NGC 3516 was monitored during 1993 February 16- May 13 by IUE every 4 days for the first month, and then every 2 days for 2 months giving a total of 40 observations. This paper gives the initial results from this campaign. (1) The broad C IV λ1549 emission line variations are delayed relative to those of the ionizing continuum…
The Ultraviolet Spectra of the Jovian Aurora
Dalgarno, A.; Liu, Weihong
The ultraviolet spectra of molecular hydrogen H2 due to electron impact excitation are calculated and compared with the high-resolution (0.56 Å) spectra of the Jovian aurora obtained with the Hubble Space Telescope Goddard High-Resolution Spectrograph. All the observed features are reproduced by electron impact excitation emissions of H…
Globular Clusters in the Inner Regions of NGC 5128 (Centaurus A)
Minniti, Dante; Jablonka, Pascale; Goudfrooij, Paul +2 more
We have identified 26 new globular cluster candidates in the inner 3 kpc of NGC 5128 (Centaurus A), the nearest known large galaxy that is the probable product of a merger. The clusters are selected on the basis of their structural parameters (observed core diameters and ellipticities), as measured from archival Wide Field Planetary Camera (WFPC) …
A New Look at Carbon Abundances in Planetary Nebulae. I. PB 6, HU 2--1, K648, and H4--1
Henry, R. B. C.; Kwitter, K. B.; Howard, J. W.
We introduce and describe a new long-term project whose goal is to employ final archived lUE spectra to study carbon abundances in a sample of planetary nebulae representing a broad range in progenitor mass and metallicity In this paper we report on initial results for PB 6, Hu 2-1, K648, and H4-1. Our UV line strengths for H4-1 are the first such…
Hubble Space Telescope Observations of the Post-- Core-Collapse Globular Cluster NGC 6752: A Search for Cataclysmic Variables
Bailyn, Charles D.; Cool, Adrienne M.; Grindlay, Jonathan E. +4 more
We report the results of HST WFPC2 observations of the core of NGC 6752. We identify two candidate cataclysmic variables (CVs) from their strong narrowband H alpha emission, periodic variability, and, in one case, a UV excess. We interpret the variability of these stars as being double-peaked, ellipsoidal light curves, in which case the orbital pe…
A New Look at Carbon Abundances in Planetary Nebulae. II. BB 1, NGC 650, NGC 1535, NGC 2440, and NGC 7027
Henry, R. B. C.; Kwitter, K. B.
This paper is the second in a series that reports on the outcome of a study of carbon abundances in a carefully chosen sample of planetary nebulae representing a large range in progenitor mass and metallicity. We use the Final Archive lUE database containing consistently reduced lUE spectra to measure line strengths of C III] λ1909, along with num…
Astro-2 Observations of Interstellar Dust and Gas in the Large Magellanic Cloud
Clayton, Geoffrey C.; Wolff, Michael J.; Davidsen, Arthur F. +5 more
This paper presents the first UV (1400-3200 A) polarimetry and far-UV (950-1200 A) spectrophotometry ever obtained for reddened stars in the Large Magellanic Cloud (LMC). We derive the UV wavelength dependence of interstellar polarization down to 1400 A and that of extinction down to near the Lyman limit. We also measure column densities of H_2_ a…
Hubble Space Telescope and Ground-based Imaging of the Bipolar Proto--Planetary Nebula M1-92: Evidence for a Collimated Outflow
Trammell, Susan R.; Goodrich, Robert W.
We present ground-based and Hubble Space Telescope narrowband images of M1-92. M1-92 is a bipolar proto--planetary nebula currently undergoing the transition from asymptotic giant branch star to planetary nebula. Previous spectropolarimetry of this object revealed that the line emission produced in the bipolar lobes is dominated by shock emission.…
Very Blue Stars and Mass Segregation in the Core of M15
Paresce, Francesco; de Marchi, Guido
The core of the globular cluster M15 (NGC 7078) has been observed with the COSTAR-corrected Faint Object Camera on board the Hubble Space Telescope (HST), through medium-band ultraviolet filters centered at 255 nm and 348 nm. A total of about 1200 stars are detected in a region of size 7" x 7" located just west of the cluster center, to form a col…
Distant Ring Galaxies as Evidence for a Steeply Increasing Galaxy Interaction Rate with Redshift
Da Costa, G. S.; Seitzer, Patrick; Walker, Alistair R. +2 more
Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) images of the Local Group dwarf galaxy Tucana reveal an unbiased sample of distant field galaxies. While a large number of these galaxies can be classified according to standard Hubble types, a significant number of these galaxies can be identified as "ring" galaxies, a morphology likely…