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HIPPARCOS Subdwarf Parallaxes: Metal-rich Clusters and the Thick Disk
Reid, Neill
We have used main-sequence fitting to calibrate the distances to the globular clusters NGC 6397, M5, NGC 288, M71, and 47 Tucanae, matching the cluster photometry against data for subdwarfs with precise Hipparcos parallax measurements and accurate abundance determinations. Both the cluster and subdwarf abundance scales are tied to high-resolution …
The Resolved Stellar Population of the Poststarburst Galaxy NGC 1569
Leitherer, Claus; Clampin, Mark; Nota, Antonella +4 more
We present Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) photometry of the resolved stellar population in the poststarburst galaxy NGC 1569. The color-magnitude diagram (CMD) derived in the F439W and F555W photometric bands contains ~2800 stars with a photometric error of <=0.2 mag down to mF439, mF555…
New Constraints on the Continuum Emission Mechanism of Active Galactic Nuclei: Intensive Monitoring of NGC 7469 in the X-Ray and Ultraviolet
Malkan, M. A.; Nandra, K.; Clavel, J. +5 more
We have undertaken near-continuous monitoring of the Seyfert 1 galaxy NGC 7469 in the X-ray with RXTE over a ~30 day baseline. The source shows strong variability with a root mean square (rms) amplitude of ~16% and peak-to-peak variations of a factor of order 2. Simultaneous data over this period were obtained in the ultraviolet (UV) using IUE, ma…
Hubble Space Telescope Goddard High Resolution Spectrograph Observations of the Be + sdO Binary φ Persei
Gies, Douglas R.; Peters, Geraldine J.; Ferrara, Elizabeth C. +4 more
Mass transfer during the evolution of intermediate-mass stars in a close binary system can result in a rejuvenated and spun-up secondary star (which may appear as a rapidly rotating Be star) orbiting an unseen, stripped-down, remnant companion. One of the best candidates for such a system is the long-period (127 days) binary φ Per. Here we present…
Quantitative Morphology of Galaxies in the Hubble Deep Field
Simard, Luc; Marleau, Francine R.
We measure quantitative structural parameters of galaxies in the Hubble deep field (HDF) on the drizzled F814W images. Our structural parameters are based on a two-component surface brightness made up of a Sérsic profile and an exponential profile. We compare our results to the visual classification of van den Bergh et al. and the C-A classificati…
Resolved 200mu M images of nearby galaxies - evidence for an extended distribution of cold dust
Bianchi, S.; Gear, W.; Davies, J. I. +6 more
We present resolved 200mu m images for 8 nearby galaxies observed with the Infrared Space Observatory (ISO). By comparing the 200mu m observations with IRAS 60mu m and 100mu m data, we find that cold dust becomes more dominant at larger radii. We infer a grain temperature of 18-21 K for this cold component i.e. about 10 K lower than the warm dust …
How many low-mass stars do destroy (3) He?
Charbonnel, C.; Do Nascimento, J. D., Jr.
We recall the current status of the long-standing (3) He problem, and its possible connection with chemical anomalies on the red giant branch. In this context, we collect in the literature all the available observations of the carbon isotopic ratio in field and cluster giant stars. Using the HIPPARCOS parallaxes, we get constraints on the evolutio…
Broad P V Absorption in the QSO PG 1254+047: Column Densities, Ionizations, and Metal Abundances in Broad Absorption Line Winds
Hamann, Fred
This paper discusses the detection of P V λλ1118, 1128 and other broad absorption lines (BALs) in archival Hubble Space Telescope spectra of the low-redshift BAL QSO PG 1254+047. The P V identification is secured by excellent redshift and profile coincidences with the other BALs, such as C IV λλ1548, 1550 and Si IV λλ1393, 1403, and by photoioniza…
Heliospheric tomography using interplanetary scintillation observations 2. Latitude and heliocentric distance dependence of solar wind structure at 0.1-1 AU
Jackson, B. V.; Tokumaru, M.; Kojima, M. +4 more
Interplanetary scintillation is a useful means to measure the solar wind in regions inaccessible to in situ observation. However, interplanetary scintillation measurements involve a line-of-sight integration, which relates contributions from all locations along the line of sight to the actual observation. We have developed a computer assisted tomo…
Exploring Cluster Elliptical Galaxies as Cosmological Standard Rods
Saglia, R. P.; Bender, Ralf; Greggio, Laura +4 more
We explore the possibility of calibrating massive cluster elliptical galaxies as cosmological standard rods using the fundamental plane relation combined with a correction for luminosity evolution. Although cluster ellipticals certainly formed in a complex way, their passive evolution out to redshifts of about 1 indicates that basically all major …