Search Publications
The Center of the Core-Cusp Globular Cluster M15: CFHT and HST Observations, ALLFRAME Reductions
Stetson, Peter B.
The central brightness cusps seen in some globular clusters are thought to be the relics of a gravothermal core collapse that occurred in the clusters' past. Recent observations show that the centers of such clusters are bluer than their outskirts, indicating that the stellar populations there are somehow different than those farther out, presumab…
Removing Cosmic-Ray Hits from Multi-Orbit HST Wide Field Camera Images
Windhorst, Rogier A.; Franklin, Barbara E.; Neuschaefer, Lyman W.
We present an optimized algorithm that removes cosmic rays ("CRs") from multi-orbit HST Wide Field/Planetary Camera ("WF/PC") images. It computes the image noise in every iteration from the WF/PC CCD equation. This includes all known sources of random and systematic calibration errors. We test this algorithm on WF/PC stacks of 2-12 orbits as a fun…
The Spectrum of the Planetary Nebula IC 418
Feibelman, Walter A.; Hyung, Siek; Aller, Lawrence H.
A detailed high spectral resolution study of the spectrum of IC 418 is made for the region 3650A to 10050A, using the Hamilton echelle spectrograph of Lick Observatory, and of the UV spectral region with archival International Ultraviolet Explorer (IUE) data. From the high resolution images in both the near- and mid-infrared, Hora et al. (1993) sh…
The HST Quasar Absorption Line Key Project VIII. CCD Imaging of Hubble Space Telescope Quasar Fields
Maoz, Dan; Schneider, Donald P.; Sargent, W. L. W. +4 more
We present an analysis of CCD images of more than 100 quasars; many of the objects have been or will be observed in the HST Key Project Quasar Absorption Line Survey. The data set consists of B, g, and i photometry of 117 quasars and deeper g (limiting magnitude of ~22) images of 101 quasar fields. Positions accurate to ~1", measured with the Spac…
Follow-Up Observations of the Remarkable Double-Degenerate Binary LB 11146
Glenn, Jason; Liebert, James; Schmidt, Gary D.
LB 11146 is a double-degenerate binary system consisting of two white dwarfs of very similar mass and surface temperature, but widely different magnetic field strengths. In an attempt to contrain the possible evolutionary tracks of the object, time-series H-alpha spectroscopy and the DA component was obtained with a time resolution as high as 11.5…
Astrometry with Hubble Space Telescope Fine Guidance Sensor Number 3: Position Mode Stability and Precision
Benedict, G. F.; Franz, O. G.; Hemenway, P. D. +11 more
We report results from a test exploring the long- and short-term astrometric stability of Hubble Space Telescope Fine Guidance Sensor #3. A test field was observed 40 times over 522 days to determine the precision and accuracy of FGS astrometry and to measure the character and magnitude of possible secular scale changes. We examine the astrometric…
Correlated Optical and Radio Structure in the QSO 1302-102
Hutchings, J. B.; Morris, S. C.; Lister, M. L. +1 more
We present new optical imaging in two broad-band colors ofthe z=0.29 bright QSO 1302-102, obtained with the Wide Field Camera of the Hubble Space Telescope. We have performed deconvolution on the HST data, previously published CFHT HRCam data, and the combined data. The structure and brightness are measured of an extended knot 2.3 arcsec from the …
X-ray Planetary Nebulae
Feibelman, Walter A.
A study of IUE archival low-dispersion spectra was conducted in an attempt to correlate the C IV/He II and C III]/C IV emission line ratios as indicators of x-ray emission in planetary nebulae. The presence of P Cygni lines revealed a strong correlation for planetaries known to exhibit x-ray emission. Of the twelve planetaries definitely known to …
HST Imaging of the Large Magellanic Cloud: The Field Star Population near 30 Doradus
Forbes, Duncan A.; Elson, Rebecca A. W.; Gilmore, Gerard F.
We present deep color-magnitude diagrams for two fields in the Large Magellanic Cloud, located about 6 arcminutes from 30 Doradus. The data are from images taken with the Hubble Space Telescope's Wide Field Camera, as part of the Medium Deep Survey Key Project. We describe a procedure for measuring stellar magnitudes in relatively crowded HST imag…
On Planetary-Nebula Nuclei of the Spectral Type `Continuous'
Feibelman, Walter A.
A detailed reexamination of existing and new IUE low- and high-resolution spectra, plus a search of recent literature, shows that for most of the central stars of planetary nebulae the spectral classification previously called "continuous type" does not really exist. The stellar continua show primarily photospheric absorption features of N V, O V,…