Search Publications
Detectability and incidence of E+A galaxies in the distant cluster Cl0939+472 (z=0.41).
Belloni, P.; Bruzual, A. G.; Thimm, G. J. +1 more
We present results of a study of E+A galaxies in the cluster Cl0939+472 (z=0.41). We have used a series of narrow-band filters (FWHM=~90-200A) covering the range from 3800 to 9200A, and broad band B, R, I filters to obtain low resolution spectra for all galaxies brighter than R=22.5mag in a 5x5' cluster field. Two of the narrow-band filters have b…
The Incidence of Damped LY alpha Systems in the Redshift Interval 0 < Z < 4
Turnshek, David A.; Rao, Sandhya M.; Briggs, Franklin H.
The determination of the incidence and column density distribution of damped Lyα systems from QSO absorption-line surveys in the redshift interval 0 < z < 1.65 is crucial for constraining the evolution of neutral gas in galaxies. This redshift interval corresponds to a time interval of ∼62% of the age of the universe for q0 = 0 (7…
Phase-retrieval analysis of pre-and post-repair Hubble Space Telescope images
Krist, John E.; Burrows, Christopher J.
Phase-retrieval measurements of point-spread functions from the pre- and post-repair Hubble Space Telescope are presented. The primary goal was to determine the aberrations present in the second wide-field and planetary camera (WFPC2) to align and validate its corrective optics. With both parametric model-fitting techniques and iterative (Gerchber…
New "Einstein Cross" Gravitational Lens Candidates in Hubble Space Telescope WFPC2 Survey Images
Im, Myungshin; Griffiths, Richard E.; Ratnatunga, Kavan U. +1 more
We report the serendipitous discovery of "Einstein cross" gravitational lens candidates using the Hubble Space Telescope (HST). We have so far discovered two good examples of such lenses, each in the form of four faint blue images located in a symmetric configuration around a red elliptical galaxy. The high resolution of HST has facilitated the di…
The Mass Ratios of Cepheid Binaries
Evans, Nancy Remage
The distribution of mass ratios in binary systems is important for comparison with star formation calculations but has been difficult to obtain observationally. This study uses IUE spectra of the hot companions of classical Cepheids with observed orbital motion to determine the companion types and hence their masses. Combining these with Cepheid m…
Of-Type Stars HD 16691 and HD 190429 Show WN-like Spectra in Infrared K Band
Conti, Peter S.; Morris, Patrick W.; Willis, Allan J. +2 more
We present 2 micrometer K-band spectra of two early-type Of stars that have infrared emission-line morphology similar to that of WN stars. Archival International Ultraviolet Explorer (IUE) spectra of these two stars indicate they appear to be Of type, rather than WN. Recently acquired optical spectra of these stars are quantitatively similar to th…
High-Speed Photometer Observations of the LMC Pulsar B0540-69
Dolan, J. F.; Boyd, P. T.; Nelson, M. J. +6 more
The High-Speed Photometer (HSP) on board the Hubble Space Telescope (HST) observed the 50 ms pulsar B0540-69 in the Large Magellanic Cloud on 1993 August 26 for 1 hr in a passband extending from 1600 Å to 7000 Å. The pulse profile resembles both that in the optical region alone and in the X-ray region. The pulsed fraction in the UV-plus-visible pa…
Fundamental parameters of Wolf-Rayet stars. V. The nature of the WN/C star WR 8.
Crowther, P. A.; Willis, A. J.; Smith, L. J.
A detailed study has been carried out on the Galactic WN/C star WR 8 (HD62910), based on ultraviolet, optical and infrared spectroscopy. Our standard model analysis allows a determination of its stellar parameters and chemical abundances of hydrogen, helium, carbon, nitrogen and oxygen. We find that the WN and WC spectral features are consistent w…
Possible detection of a diffuse interstellar cloud boundary. II. HST-GHRS observations of Sirius A.
Ferlet, R.; Vidal-Madjar, A.; Lallement, R. +2 more
We present HST-GHRS observations with the G160M grating in the HI Lyman α spectral range toward Sirius A and around the Civ 1550 A doublet toward three lines of sight of the local interstellar medium. The local interstellar cloud (LIC) in which the Sun is embedded and another cloud (BC) are detected toward Sirius A from high spectral resolution Mg…
Interaction of a Stellar Wind with Clumpy Stellar Ejecta in A30
Borkowski, Kazimierz J.; Tsvetanov, Zlatan I.; Harrington, J. Patrick
Clumpy, hydrogen-depleted material in the planetary nebula Abell 30 was ejected by its central star ~1000 yr ago. We present observations of Abell 30 showing compact, hydrogen-poor knots with wind-blown tails, obtained with the Wide Field Planetary Camera (WFPC2) on board the Hubble Space Telescope, which offer an unprecedented view of the interac…