Search Publications
SN 1991bg: A Type IA Supernova With a Difference
Suntzeff, N. B.; Walker, A. R.; Caldwell, Nelson +28 more
We present 13 spectra and 31 photometric observations covering the first 150 days of SN 1991bg in NGC 4374 (M 84). Although SN 1991bg was a type Ia supernova displaying the characteristic Si II absorption at 6150 A near maximum and the Fe emission lines at late phases, it varied from the well-defined norm for SNe Ia in several important respects. …
Hubble Space Telescope Discovery of Candidate Young Globular Clusters in the Merger Remnant NGC 7252
Robert, Carmelle; Leitherer, Claus; Whitmore, Bradley C. +2 more
New, high-resolution images of the central region of NGC 7252 obtained with the Planetary Camera of the Hubble Space Telescope are presented. NGC 7252 (sometimes referred to as the "Atoms-for-Peace" Galaxy) is a prototypical example of a remnant of two merged disk galaxies. Our most striking result is the discovery of a population of about 40 blue…
Planetary Camera Observations of the Double Nucleus of M31
Holtzman, J. A.; Faber, S. M.; Ewald, S. P. +13 more
V- and I-band HST Planetary Camera images of the great spiral galaxy in Andromeda, M31, show that its inner nucleus consists of two components separated by 0.49". The outer isophotes of the nucleus at 1.4" < r < 3.0" are elongated, but are concentric with the M31 bulge. The nuclear component with the lower surface brightness, P2, is also coi…
High Resolution Imaging of Galaxy Cores
Boksenberg, A.; Barbieri, C.; Weigelt, G. +17 more
Surface photometry data obtained with the Faint Object Camera of the Hubble Space Telescope in the cores of ten galaxies is presented. The major results are: (i) none of the galaxies show truly "isothermal" cores, (ii) galaxies with nuclear activity show very similar light profiles, (iii) all objects show central mass densities > 10^3^M_sun_ pc…
Stellar Kinematic Groups. I. The URSA Major Group
Soderblom, David R.; Mayor, Michel
The Ursa Major Group (UMaG) is studied as a test case for the authenticity of Stellar Kinematic Groups, using Coravel radial velocities, recent compilations of astrometric data, and new spectroscopic observations. Spectroscopic age indicators, particularly indices of the strength of chromospheric emission, are applied to solar-type candidate membe…
Evolution of the Symbiotic Binary System AG Pegasi: The Slowest Classical Nova Ever Recorded
Polidan, Ronald S.; Mikolajewska, Joanna; Slovak, Mark H. +2 more
We present an analysis of new and existing photometric and spectroscopic observations of the ongoing eruption in the symbiotic star AG Pegasi, showing that this binary has evolved considerably since the turn of the century. Recent dramatic changes in both the UV continuum and the wind from the hot component allow a more detailed analysis than in p…
Wide Field Camera Observations of Baade's Window
Faber, S. M.; Holtzman, Jon A.; O'Neil, Earl J., Jr. +7 more
We have observed a field in Baade's Window using the Wide Field Camera (WFC) of the Hubble Space Telescope (HST) and obtain V- and I-band photometry down to V approximately 22.5. These data go several magnitudes fainter than previously obtained from the ground. The location of the break in the luminosity function suggests that there are a signific…
The Early Ultraviolet Spectral Evolution of Nova Cygni 1992
Ake, T. B.; Shore, Steven N.; Sonneborn, George +2 more
We report on the high resolution ultraviolet line profile evolution of Nova Cygni 1992 using the International Ultraviolet Explorer (IUE) satellite and the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST). Our observations cover the period from discovery in 1992 February through 1993 April. The initial expansion velo…
A Hubble Space Telescope Planetary Camera View of Giant H II Regions: The Wolf-Rayet Content of NGC 595 and NGC 604 in M33
Drissen, Laurent; Moffat, Anthony F. J.; Shara, Michael M.
We present images of NGC 595 and NGC 604, the most massive giant H II regions in M33, obtained with the Planetary Camera aboard the Hubble Space Telescope in order to study their Wolf-Rayet (WR) population. Fourteen WR and/or Of candidates are detected in NGC 604, and eleven in NGC 595. All previously claimed "superluminous" WR stars are found to …
Gravitational Lensing Statistics Based on a Large Sample of Highly Luminous Quasars
Magain, P.; Filippenko, A. V.; Surdej, J. +6 more
Results on gravitational lensing statistics applied to a sample of 469 highly luminous quasars are reported. The objects were directly imaged, either from the ground (ESO, CFH) under optimal seeing conditions, or using the Hubble Space Telescope. We have derived values for the effectiveness parameter F of galaxies, modeled by means of singular iso…