Search Publications
Discovery of z = 0.0912 and z = 0.2212 Damped Lyα Absorption-Line Systems Toward the Quasar OI 363: Limits on the Nature of Damped Lyα Galaxies
Turnshek, David A.; Rao, Sandhya M.
The discovery of a zabs=0.0912 damped Lyα absorption-line system in the Hubble Space Telescope Faint Object Spectrograph ultraviolet spectrum of the quasar OI 363 (0738+313) is reported. This is the lowest redshift quasar-damped Lyα system known. Its neutral hydrogen column density is N(H I) =1.5+/-0.2×1021 atoms cm-2
A Search for Star Clusters from the HIPPARCOS Data
van Leeuwen, Floor; Kozhurina-Platais, Vera; Platais, Imants
We present results of a search for nearby star clusters and associations using Hipparcos Catalogue data, restricting the sample to stars with parallaxes above 2 mas (d <~ 500 pc). Two new OB associations have been identified in the Carina-Vela and Cepheus-Cygnus-Lyra-Vulpecula regions. A very probable new open cluster has been discovered in Car…
The Kinematic Composition of Mg II Absorbers
Charlton, Jane C.; Churchill, Christopher W.
The study of galaxy evolution using quasar absorption lines requires an understanding of what components of galaxies and their surroundings are contributing to the absorption in various transitions. This paper considers the kinematic composition of the class of 0.4 < z < 1.0 Mg II absorbers, particularly addressing the question of what fract…
Nearby Young Solar Analogs. I. Catalog and Stellar Characteristics
Gaidos, Eric J.
We present a catalog of 38 young solar analogs within 25 pc, stars that are uniquely well suited for observations of their circumstellar environments to improve our understanding of conditions within the solar system during the Hadean/early Archean eons (prior to 3.8 Gyr ago). These G and early K stars were selected from the Hipparcos astrometric …
Non-Maxwellian Redistribution in Solar Coronal Lyα Emission
Cranmer, Steven R.
This paper presents theoretical models of H I Lyα emission from the extended solar corona, taking into account various plasma kinetic effects that induce departures from Maxwellian velocity distributions. Such phenomena as suprathermal tails, strong temperature anisotropies, and skewed or double-peaked distributions have been observed in the solar…
An Optical/Near-Infrared Study of Radio-loud Quasar Environments. II. Imaging Results
Hall, Patrick B.; Green, Richard F.
We have previously reported a significant excess of K >~ 19 galaxies in the fields of a sample of 31 z = 1-2 quasars (Hall, Green, & Cohen). Here we examine the properties of this excess galaxy population using optical and near-IR imaging. The excess occurs on two spatial scales. One component lies at θ < 40" from the quasars and is sign…
Evidence for a signature of the galactic bar in the solar neighbourhood
Udry, S.; Raboud, D.; Grenon, M. +2 more
Using available kinematical data for a subsample of NLTT stars from the HIPPARCOS mission we confirm the existence of a previously reported local anomaly in the (u,v) plane: the mean motion /line{u} for old disc stars, with v < -30 km s(-1) , is largely positive (+19 +/- 9 km s(-1) w.r.t. the Galactic Center). With the use of the newest global …
The Rapid Decay of the Optical Emission from GRB 980326 and Its Possible Implications
Piro, L.; Veilleux, S.; Pian, E. +39 more
We report the discovery of the optical counterpart to GRB 980326. Its rapid optical decay can be characterized by a power law with exponent -2.10+/-0.13 and a constant underlying source at Rc=25.5+/-0.5. Its optical colors 2.1 days after the burst imply a spectral slope of -0.66+/-0.70. The γ-ray spectrum as observed with BATSE shows th…
Properties of the quiet Sun EUV network
Keenan, F. P.; Phillips, K. J. H.; Gallagher, P. T. +1 more
Observations of the quiet Sun network in a small region at Sun centre taken with the Coronal Diagnostic Spectrometer (CDS) on board SOHO are reported for EUV lines with T_e between ~ 10(4) and 10(6) K. The changing structure of the network in the upper chromosphere, transition region, up to the corona was examined using intensity distributions whi…
The binary star population of the young cluster NGC 1818 in the Large Magellanic Cloud
Gilmore, Gerard; Elson, Rebecca A. W.; Sigurdsson, Steinn +2 more
We determine the binary star fraction as a function of radius in NGC 1818, a young rich cluster in the Large Magellanic Cloud, using Hubble Space Telescope images in bands F336W (~U) and F555W (~V). Our sample includes binaries with M_primary~2-5.5M_solar and M_secondary>~0.7M_primary. The binary fraction increases towards the cluster centre, f…