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Near-coeval formation of the Galactic bulge and halo inferred from globular cluster ages
Gilmozzi, Roberto; Rich, R. Michael; Renzini, Alvio +4 more
THE morphology of our Galaxy is characterized by a disk of stars moving on circular orbits, surrounding a central spheroidal body of stars on high-velocity, randomly oriented orbits. The spheroid is further differentiated into an inner bulge and an outer halo; the bulge stars are rich in elements heavier than helium ('metals'), whereas the halo st…
Optical and Ultraviolet Analyses of ZZ Ceti Stars and Study of the Atmospheric Convective Efficiency in DA White Dwarfs
Fontaine, G.; Bergeron, P.; Wesemael, F. +3 more
New high signal-to-noise optical spectrophotometry is presented for 22 ZZ Ceti stars. The atmospheric parameters (Teff log g) and the mass are derived for each object using new model atmospheres and synthetic spectra calculated within the mixing-length theory, as well as recent published mass-radius relationships. Various parameterizati…
The Gaseous Extent of Galaxies and the Origin of Lyman-Alpha Absorption Systems: A Survey of Galaxies in the Fields of Hubble Space Telescope Spectroscopic Target QSOs
Bowen, David V.; Lanzetta, Kenneth M.; Webb, John K. +1 more
We present initial results of an imaging and spectroscopic survey of faint galaxies in fields of Hubble Space Telescope spectroscopic target QSOs. The primary objectives of the survey are (1) to determine the incidence, extent, and covering factor of extended gaseous envelopes of luminous galaxies and (2) to determine the fraction of Lyα absorptio…
Detection of an oxygen atmosphere on Jupiter's moon Europa
Feldman, P. D.; Strobel, D. F.; Weaver, H. A. +2 more
EUROPA, the second large satellite out from Jupiter, is roughly the size of Earth's Moon, but unlike the Moon, it has water ice on its surface1. There have been suggestions that an oxygen atmosphere should accumulate around such a body, through reactions which break up the water molecules and form molecular hydrogen and oxygen2,3
VIRGO: Experiment for Helioseismology and Solar Irradiance Monitoring
Gough, Douglas; Chevalier, André; Domingo, Vicente +22 more
The scientific objective of the VIRGO experiment (Variability of solar IRradiance and Gravity Oscillations) is to determine the characteristics of pressure and internal gravity oscillations by observing irradiance and radiance variations, to measure the solar total and spectral irradiance and to quantify their variability over periods of days to t…
Ulysses solar wind plasma observations from pole to pole
McComas, D. J.; Goldstein, B. E.; Bame, S. J. +8 more
We present Ulysses solar wind plasma data from the peak southerly latitude of -80.2° on 12 September 1994 through the corresponding northerly latitude on 31 July 1995. Ulysses encountered fast wind throughout this time except for a 43° band centered on the solar equator. Median mass flux was nearly constant with latitude, while speed and density h…
Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. VIII. an Intensive HST, IUE, and Ground-based Study of NGC 5548
Veilleux, S.; Shull, J. M.; Malkan, M. A. +109 more
We present the data and initial results from a combined HST/IUE/groundbased spectroscopic monitoring campaign on the Seyfert 1 galaxy NGC 5548 that was undertaken in order to address questions that require both higher temporal resolution and higher signal-to-noise ratios than were obtained in our previous multiwavelength monitoring of this galaxy …
Origin of the Solar Wind From Composition Data
Geiss, J.; Gloeckler, G.; von Steiger, R.
The ESA/NASA spacecraft Ulysses is making, for the first time, direct measurements in the solar wind originating from virtually all places where the corona expands. Since the initial two polar passes of Ulysses occur during relatively quiet solar conditions, we discuss here the three main regimes of quasi-stationary solar wind flow: the high speed…
Global Oscillations at Low Frequency from the SOHO Mission (GOLF)
Damé, L.; García, R. A.; Pallé, P. L. +28 more
The GOLF experiment on the SOHO mission aims to study the internal structure of the sun by measuring the spectrum of global oscillations in the frequency range 10−7 to 10−2 Hz. Bothp andg mode oscillations will be investigated, with the emphasis on the low order long period waves which penetrate the solar core. The instrument…
The Heliospheric Magnetic Field Over the South Polar Region of the Sun
Balogh, A.; Tsurutani, B. T.; Horbury, T. S. +3 more
Magnetic field measurements from the Ulysses space mission over the south polar regions of the sun showed that the structure and properties of the three-dimensional heliosphere were determined by the fast solar wind flow and magnetic fields from the large coronal holes in the polar regions of the sun. This conclusion applies at the current, minimu…