Search Publications
Testing the White Dwarf Mass-Radius Relation with HIPPARCOS
Provencal, J. L.; Shipman, H. L.; Thejll, P. +1 more
We present the Hipparcos parallaxes and resulting radii for 10 white dwarfs in visual binaries or common proper-motion systems and 11 field white dwarfs. For bright stars, Hipparcos parallaxes have uncertainties approaching 1 mas and are thus considerably more accurate than earlier ground-based parallaxes. Overall, our results support the predicti…
The Slope of the Cluster Elliptical Red Sequence: A Probe of Cluster Evolution
Yee, H. K. C.; Kodama, Tadayuki; Gladders, Michael D. +1 more
The current formation models for cluster elliptical galaxies, which incorporate a mechanism for the metallicity enhancement of massive elliptical galaxies, predict a change in the observed slope of the red sequence of elliptical galaxies as a function of redshift. This change occurs primarily because the metal-rich galaxies become redder faster th…
Interstellar and Inner Source Pickup Ions Observed with SWICS on ULYSSES
Gloeckler, George; Geiss, Johannes
Many species of pickup ions, both of interstellar origin and from an inner, distributed source have been discovered using data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses. Velocity distribution functions of these ions were measured for the first time over heliocentric distances between 1.35 and 5.4 AU, both at high and low …
High-redshift galaxies in the Hubble Deep Field - II. Colours and number counts
Ferguson, Henry C.; Madau, Piero; Zamorani, Gianni +2 more
We discuss the deep galaxy counts from the Hubble Deep Field (HDF) imaging survey. At faint magnitudes, the slope of the differential number-magnitude relation is flatter than 0.2 in all four HDF bandpasses. In the ultraviolet, a fluctuation analysis shows that the flattening observed below U_300~26 mag is not caused by incompleteness and is more …
Crystalline silicates in planetary nebulae with [WC] central stars
de Graauw, Th.; Waters, L. B. F. M.; Pottasch, S. R. +6 more
We present ISO-SWS spectroscopy of the cool dusty envelopes surrounding two Planetary Nebulae with [WC] central stars, BD+30 3639 and He 2-113. The lambda < 15 mu m region is dominated by a rising continuum with prominent emission from C-rich dust (PAHs), while the long wavelength part shows narrow solid state features from crystalline silicate…
The ACT Reference Catalog
Urban, S. E.; Wycoff, G. L.; Corbin, T. E.
The US Naval Observatory has completed the compilation of the ACT Reference Catalog, containing 988,758 stars covering the entire sky. The motivation behind the ACT was to provide accurate proper motions for the majority of the stars in the Tycho Catalogue. To do this, positions from new reductions of the Astrographic Catalogue (AC 2000) were comb…
A Tentative Detection of the Cosmic Infrared Background at 3.5 µm from COBE/DIRBE Observations
Dwek, E.; Arendt, R. G.
Foreground emission and scattered light from interplanetary dust (IPD) particles and emission from Galactic stellar sources are the greatest obstacles to determining the cosmic infrared background (CIB) from diffuse sky measurements in the ~1-5 µm range. We use ground-based observational limits on the K-band intensity of the CIB in conjuncti…
Temperature Dependence of Ultraviolet Line Average Doppler Shifts in the Quiet Sun
Chae, J.; Yun, H. S.; Poland, A. I.
The existence of prevailing redshifts in the UV lines formed in the solar transition region raises an important question concerning its physical origin and its role in the mass and energy balance of the outer solar atmosphere. A series of UV spectral lines observed by SUMER has been analyzed to obtain the spatial average of Doppler shifts in the q…
HIPPARCOS subdwarfs and globular cluster ages: the distance and age of M 92
Pont, F.; Turon, C.; Mayor, M. +1 more
A new determination of the distance and age of the old globular cluster M 92 (NGC 6341) is obtained from a consideration of a set of more than 500 subdwarf candidates with Hipparcos parallaxes. Precise [Fe/H] values are derived for most stars using the equivalent width of the Coravel cross-correlation function. We examine at some length the biases…
Towards a fundamental calibration of stellar parameters of A, F, G, K dwarfs and giants
di Benedetto, G. P.
I report on the implementation of the empirical surface brightness technique using the near-infrared Johnson broadband { (V-K)} colour as suitable sampling observable aimed at providing accurate effective temperatures of 537 dwarfs and giants of A-F-G-K spectral-type selected for a flux calibration of the Infrared Space Observatory (ISO). The surf…