Search Publications
On the Nature of the Strong Emission-Line Galaxies in Cluster CL 0024+1654: Are Some the Progenitors of Low-Mass Spheroidals?
Koo, David C.; Gallego, Jesús; Wirth, Gregory D. +1 more
We present new size, line ratio, and velocity width measurements for six strong emission-line galaxies in the galaxy cluster, Cl 0024+1654, at redshift z ~ 0.4. The velocity widths from Keck spectra are all narrow (30 <~ σ <~ 120 km s-1), with three profiles showing double peaks. Four galaxies have low masses (M <~ 1010
Ultraviolet Imaging Observations of the cD Galaxy in Abell 1795: Further Evidence for Massive Star Formation in a Cooling Flow
O'Connell, Robert W.; Bohlin, Ralph C.; Smith, Andrew M. +5 more
We present images from the Ultraviolet Imaging Telescope (UIT) of the Abell 1795 cluster of galaxies. We compare the cD galaxy morphology and photometry of these data with those from existing archival and published data. The addition of a far-UV color helps us to construct and test star formation model scenarios for the sources of UV emission. Mod…
The Absence of Diffuse Gas around the Dwarf Spheroidal Galaxy Leo I
Bowen, David V.; Ferrara, Andrea; Blades, J. Chris +2 more
We have obtained spectra of three QSO/AGNs with the GHRS aboard the Hubble Space Telescope to search for absorption from low column density gas in the halo of the dwarf spheroidal (dSph) galaxy Leo I. The probe sight lines pass 2.1, 3.7, and 8.1 kpc from the center of the galaxy, but no C IV, Si II, or Si IV absorption is found at the velocity of …
Quasar Variability and Gravitational Microlensing
Taylor, A. N.; Hawkins, M. R. S.
In this Letter we examine the claim by Baganoff & Malkan that the timescale of brightness variations of quasars increases with decreasing optical wavelength, and that this effect can offset a time dilation effect at high redshift. They base their case on a thin accretion disk model that implies that timescales become shorter as the observed pa…
Boron Abundances of B Stars of the Orion Association
Gies, Douglas R.; Cunha, Katia; Lambert, David L. +2 more
The boron abundance of four B-type stars from the Orion association has been determined from Goddard High Resolution Spectrograph (GHRS)/Hubble Space Telescope (HST) spectra covering the B II 1362 Å resonance line. After correction for large non-LTE effects, the mean boron abundance is similar to the meteoritic abundance, but a factor of 4 (0.6 de…
The orbit of the supergiant component of VELA X-1 derived from IUE radial velocities
Lloyd, C.; Stickland, D.; Radziun-Woodham, A.
47 short-wavelength, high-resolution IUE spectra have been used to derive the orbital elements of HD 77581, the supergiant companion to the neutron star in the X-ray source Vela X-1; the velocity amplitude is at the lower end of the range found by previous workers using primarily optical spectra, but other elements (e, omega) are in fair agreement…
Radiative Balance and Dynamics in the Stratosphere of Jupiter: Results from a Latitude-Dependent Aerosol Heating Model
Moreno, Fernando; Sedano, José
An updated dynamical model for the circulation in the jovian stratosphere has been developed. For computation of the heating and cooling rates in the stratosphere, required to obtain the radiative flux convergence, the model makes use of exponential-sum derived coefficients from laboratory and correlated-kdistributions from line listing data for t…
HIPPARCOS distances of X-ray selected stars: implications on their nature as stellar population.
Micela, G.; Favata, F.; Sciortino, S.
We present the parallaxes, measured by Hipparcos, for a sample of X-ray selected stars. The stars belong to the stellar sample of the Einstein Extended Medium Sensitivity Survey. They are all at galactic latitude |b|>20deg, and are generally far away from known star forming regions. Several of these stars show lithium abundance and activity lev…
Wide Field Planetary Camera 2 Photometry of the Bright, Mysterious White Dwarf Procyon B
Provencal, J. L.; Bergeron, P.; Sion, E. M. +4 more
Procyon B is one of a select group of white dwarf stars which are members of visual binary systems and represents a critically important object for testing the fundamental physics of stellar degeneracy. We have accurate measurements of the binary period and the white dwarf mass. However, the extreme brightness ratio and the small separation betwee…
High Spatial Resolution Near-Infrared Imaging of the Central Regions of M31
Doyon, R.; Davidge, T. J.; Rigaut, F. +1 more
H and K images with 0.15 arc sec angular resolution are used to probe the stellar content in the central 8 arcsec of M31. A large number of stars are detected, and the majority of these have K≥17.5 and H - K colors between 0 and 1. After correcting for differences in distance and reddening, the mean locus of the M31 (K,H- K) diagram is found to be…