Search Publications
Detection of Interstellar CH3
Feuchtgruber, H.; van Dishoeck, E. F.; Helmich, F. P. +1 more
Observations with the Short Wavelength Spectrometer on board the Infrared Space Observatory have led to the first detection of the methyl radical CH3 in the interstellar medium. The ν2 Q-branch at 16.5 µm and the R(0) line at 16.0 µm have been unambiguously detected toward the Galactic center Sagittarius A*. The a…
Tomography of the Solar Corona. I. A Robust, Regularized, Positive Estimation Method
Frazin, Richard A.
A general method for the reconstruction of emissivity structures in the solar corona from projection data is presented. The method creates a robust, regularized, positive estimate (RRPE) of the coronal emissivity distribution. The problem of reconstructing the three-dimensional emissivity from a time series of coronagraph images is considered in d…
NICMOS Imaging of the Damped Lyα Absorber at Z=1.89 toward LBQS 1210+1731: Constraints on Size and Star Formation Rate
Schneider, Glenn; Rieke, Marcia J.; Kulkarni, Varsha P. +5 more
We report results of a high-resolution imaging search for the galaxy associated with the damped Lyα (DLA) absorber at z=1.892 toward the zem=2.543 quasar LBQS 1210+1731, using the Hubble Space Telescope (HST) NICMOS. The images were obtained in the broad filter F160W and the narrow filter F190N with camera 2 on NICMOS and were aimed at …
Evidence of Interstellar NA I Structure at Scales Down to 15 AU in Low-Density Gas
Meyer, David M.; Blades, J. C.; Lauroesch, J. T.
We present high-resolution Hubble Space Telescope/Space Telescope Imaging Spectrograph and multiepoch KPNO coudé feed observations of multiple interstellar lines toward the binary system HD 32039/40. Comparisons of the Na I profiles observed over a period of 4.25 yr reveal significant temporal variation in the Na I column in at least one component…
Two K Giants with Supermeteoritic Lithium Abundances: HDE 233517 and HD 9746
Henry, Gregory W.; Fekel, Francis C.; Uitenbroek, Han +1 more
Two unusual Li-rich K giants, HDE 233517 and HD 9746, have been studied. Optical spectroscopy and photometry have been obtained to determine the fundamental parameters of HDE 233517, a single K2 III with an extremely large infrared excess. The spectra yield Teff=4475 K, logg=2.25, [Fe/H]=-0.37, vsini=17.6 km s-1, and a non-LT…
α Centauri AB
Guenther, D. B.; Demarque, P.
Detailed models of α Centauri A and B based on the Hipparcos, Yale, and Söderhjelm parallaxes are compared. The consequences of the uncertainty in mass, luminosity, surface temperature, and composition on the structure and the p-mode pulsation spectrum of the models are presented. All of the models were constructed using the most current stellar s…
The Relative Age of the Thin and Thick Galactic Disks
Chaboyer, Brian; Liu, Wilson M.
We determine the relative ages of the open cluster NGC 188 and selected Hipparcos field stars by isochrone fitting and compare them to the age of the thick-disk globular cluster 47 Tuc. The best-fit age for NGC 188 was determined to be 6.5+/-1.0 Gyr. The solar-metallicity Hipparcos field stars yielded a slightly older thin-disk age, 7.5+/-0.7 Gyr.…
A New Look at Carbon Abundances in Planetary Nebulae. IV. Implications for Stellar Nucleosynthesis
Henry, R. B. C.; Kwitter, K. B.; Bates, J. A.
This paper is the fourth and final report on a project designed to study carbon abundances in a sample of planetary nebulae representing a broad range in progenitor mass and metallicity. We present newly acquired optical spectrophotometric data for three Galactic planetary nebulae, IC 418, NGC 2392, and NGC 3242, and combine them with UV data from…
A Self-occulting Accretion Disk in the SW Sextantis Star DW Ursae Majoris
Dhillon, V. S.; Szkody, Paula; Hoard, D. W. +2 more
We present the ultraviolet spectrum of the SW Sextantis star and nova-like variable DW Ursae Majoris in an optical low state, as observed with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope (HST). The data are well described by a synthetic white dwarf (WD) spectrum with Teff=46,000+/-1000 K, logg=7.60+/-0.1…
Spectroscopic Abundances in Cool Pleiades Dwarfs and NGC 2264 Stars
Soderblom, David R.; King, Jeremy R.; Jones, Burton F. +1 more
We derive parameters and abundances of several elements in two cool Pleiades dwarfs, four cool NGC 2264 pre-main-sequence stars, and a probable NGC 2264 nonmember from high-resolution, moderate signal-to-noise ratio, Keck/HIRES spectra. Our Pleiades Fe abundance agrees with previous spectroscopic and photometric values of hotter stars and does not…