Search Publications
The Accretion Disk and White Dwarf in the U Geminorum type Dwarf Novae UZ Serpentis and SS Aurigae during Quiescence
Sion, Edward M.; Lake, Joshua
We have carried out high-gravity model atmosphere and accretion disk synthetic spectral fits for the U Geminorum type dwarf novae during quiescence. For UZ Ser, we find that the far-UV spectrum is best fitted with a logg=8, Teff=27,000 K photosphere with abundances near solar. The best-fit accretion disk model for UZ Ser has Mwd
Investigation of Gravitational Lens Mass Models
Griffiths, Richard E.; Ratnatunga, Kavan U.; Knudson, Adam
We have previously reported the discovery of strong gravitational lensing by faint elliptical galaxies using the Wide Field Planetary Camera 2 (WFPC2) on the Hubble Space Telescope, and here we investigate their potential usefulness in placing constraints on lens mass models. We compare various ellipsoidal surface mass distributions, including tho…
The Tolman Surface Brightness Test for the Reality of the Expansion. II. The Effect of the Point-Spread Function and Galaxy Ellipticity on the Derived Photometric Parameters
Sandage, Allan; Lubin, Lori M.
To complete the Tolman surface brightness test on the reality of the expansion of the universe, we need to measure accurately the surface brightness profiles of the high-redshift galaxy sample. To quantify this accuracy, we investigate the effects of various sizes of point-spread functions composed of telescope diffraction, CCD pixel resolutions, …
Ultraviolet Observations of Triton in 1999 with the Space Telescope Imaging Spectrograph: 2150-3180 Å Spectroscopy and Disk-integrated Photometry
Stern, S. Alan; Young, Leslie A.
We observed Triton using the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) on 1999 August 28, September 11, and September 13 UT. On all three occasions, we obtained images at both 271 and 374 nm, and spectra from 215 to 318 nm. We find that Triton's geometric albedo is high through the near- and mid-UV, decreasing…
The Galactic Evolution of Beryllium and Boron Revisited
King, Jeremy R.
The largest, highest-quality, and most near-homogeneously treated extant available samples of Be, B, Fe, and O abundances are analyzed on four different stellar parameter scales, considering different O abundance indicators and deriving uncertainties in their relation with the required aid of jackknife and bootstrap simulations/resampling. Despite…
The Optical Spectroscopic Evolution of V1974 Cygni (Nova Cygni 1992)
Garnavich, Peter M.; Noriega-Crespo, Alberto; Moro-Martín, Amaya
Optical observations of V1974 Cygni (Nova Cygni 1992) spanning a 4 yr period have been used to study its spectroscopic evolution. The data cover a wavelength range from ~3200-8000 Å and follow the nebular evolutionary phase of the ejecta. We have modeled the integrated fluxes by means of the photoionization code CLOUDY. The models were run at a fi…
Archival HST and IUE Study of the Dwarf Novae AH Herculis and CM Delphini: Exposed White Dwarfs?
Wood, Janet H.; Stys, D.; Sion, E. +2 more
We have analyzed Hubble Space Telescope (HST) archival and IUE NEWSIPS archival SWP spectra of the dwarf novae CM Del and AH Her obtained when AAVSO light-curve data indicated the occurrence of dwarf nova quiescence. We have computed synthetic, high-gravity spectra in LTE with solar composition using TLUSTY195 and SYNSPEC42 and have carried out fi…
Ultraviolet Eclipse Observations and Fundamental Parameters of the Binary HR 2554 (G6 II+A1 V)
Kürster, Martin; Bennett, Philip D.; Brown, Alexander +4 more
HR 2554 is an eclipsing binary system that contains a G6 II primary star and an A dwarf secondary. We have obtained ultraviolet spectra during two eclipses of HR 2554 in 1994 March-April and 1995 May using the HST Goddard High Resolution Spectrograph (GHRS) to study the atmospheric structure of the primary and to better establish the properties of…
The Dust Temperature of the ``Dusty'' Radio Galaxy MG 1019+0535: Evidence for an Outflow
Spinrad, Hyron; Manning, Curtis
Radio galaxies characteristically have strong Lyα emission lines. However, a few have Lyα equivalent widths that are substantially weaker in relation to other emission lines. One in particular, MG 1019+0535 (z=2.765), was studied by Dey, Spinrad, & Dickinson in 1995. We report on our reduction of Infrared Space Observatory (ISO) data in the 16…
Australia Telescope Compact Array Observations of the OH Star Roberts 22: Resolved Images of Hydroxyl Emission
Goss, W. M.; Dyer, K. K.; Kemball, A. J.
We have imaged the unusual OH/IR object G284-0.8 (Roberts 22) in the OH transitions at 1612, 1665, and 1667 MHz using the Australia Telescope Compact Array in Narrabri, NSW, Australia. The angular resolution of the OH images we present here is 6" (12,000 AU at a distance of 2 kpc). We find OH emission of extent 1.5" (2800 AU) located inside the op…