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A Multiwavelength Campaign on γ Cassiopeiae. I. The Case for Surface X-Ray Flaring
Smith, Myron A.; Robinson, Richard D.; Corbet, Robin H. D.
In 1996 March we obtained simultaneous Rossi X-Ray Timing Explorer RXTE Proportional Counter Array (PCA) and Hubble Space Telescope (HST) Goddard High-Resolution Spectrograph (GHRS) light curves for the B0.5e star γ Cas in order to compare its X-ray and ultraviolet continuum flux behaviors. The GHRS data set consisted of a nearly continuous sequen…
The HIPPARCOS Hertzsprung-Russell diagram of S stars: probing nucleosynthesis and dredge-up
Jorissen, A.; Udry, S.; Mayor, M. +2 more
HIPPARCOS trigonometrical parallaxes make it possible to compare the location of Tc-rich and Tc-poor S stars in the Hertzsprung-Russell (HR) diagram: Tc-rich S stars are found to be cooler and intrinsically brighter than Tc-poor S stars. The comparison with the Geneva evolutionary tracks reveals that the line marking the onset of thermal pulses on…
The Infrared Morphology of eta Carinae
Smith, Nathan; Gehrz, Robert D.; Krautter, Joachim
We present results of a recent 2-12 µm ground-based infrared (IR) imaging study of Eta Carinae. We discuss the comparative spatial morphology of the bipolar lobes, the ``skirt'' defined by the equatorial ejecta, and the bright features in the core. We derive separate color temperature values of 200, 240, and 420 K for the bipolar lobes, skir…
Evolution of the Angular Correlation Function
Connolly, A. J.; Szalay, A. S.; Brunner, R. J.
For faint photometric surveys, our ability to quantify the clustering of galaxies has depended on interpreting the angular correlation function as a function of the limiting magnitude of the data. Because of the broad redshift distribution of galaxies at faint magnitude limits, the correlation signal has been extremely difficult to detect and inte…
On the Use of [Na/Fe] and [alpha/Fe] Ratios and Hipparcos-based (U, V, W) Velocities as Age Indicators among Low-Metallicity Halo Field Giants
Sneden, Christopher; Hanson, Robert B.; Kraft, Robert P. +1 more
We have examined the [Na/Fe] and [Mg/Fe] ratios in a sample of 68 field halo giants with -3 <~ [Fe/H] <~ -1. We recalculated the Galactic (U, V, W) velocity components for these stars, using Hipparcos proper motions and a new Hipparcos-based distance scale. We used these data to see how the abundance ratios may relate to kinematical substruc…
The Optical Gravitational Lensing Experiment. The Distance Scale: Galactic Bulge -- LMC -- SMC.
Udalski, A.
We analyze the mean luminosity of three samples of field RRab Lyr stars observed in the course of the OGLE microlensing experiment: 73 stars from the Galactic bulge and 110 and 128 stars from selected fields in the LMC and SMC, respectively. The fields are the same as in the recent distance determination to the Magellanic Clouds with the red clump…
A Study of Nine High-Redshift Clusters of Galaxies. I. The Survey
Postman, Marc; Lubin, Lori M.; Oke, J. B.
We present a description of the observations and data reduction procedures for an extensive spectroscopic and multiband photometric study of nine high-redshift, optically selected cluster candidates. The primary goal of the survey is to establish new constraints on cluster and galaxy evolution, with specific emphasis on the evolution of galaxy mor…
Variable sub-arcsecond structure in the circumstellar envelope of IRC+10216
Haniff, C. A.; Buscher, D. F.
We present new diffraction-limited interferometric images of the carbon star IRC+10216 at wavelengths of 2.2 mu m and 3.4 mu m. These show that the distribution of the near-infrared emission from the star departs significantly from a spherical geometry on 0.1 arcsecond scales. At 3.4 mu m, i.e. close to the peak of the star/dust-shell spectral ene…
Hubble Space Telescope Imaging of IRAS 17441-2411: A Case Study of a Bipolar Nebula with a Circumstellar Disk
Volk, Kevin; Kwok, Sun; Hrivnak, Bruce J. +1 more
The bipolar proto-planetary nebula IRAS 17441-2411 (the ``Silkworm Nebula'') was observed with the Hubble Space Telescope. By fitting the observed spectral energy distribution and the V-band image by a two-dimensional radiation transfer model, we derive the properties of the circumstellar wind and a proposed circumstellar ``disk.'' We suggest that…
2.12 Micron Molecular Hydrogen Emission from Circumstellar Disks Embedded in the Orion Nebula
Schneider, Glenn; Young, Erick T.; Rieke, Marcia +5 more
We present narrowband images of two externally illuminated circumstellar disks embedded in the Orion Nebula. The images were taken with camera 2 of the Near-Infrared Camera and Multiobject Spectrometer (NICMOS) as part of the Hubble Space Telescope Early Release Observations program. Molecular hydrogen emission is confined to the silhouettes embed…