Search Publications
The discovery of a new massive O-type close binary: tau CMa (HD 57061), based on HIPPARCOS and Walraven photometry
van Leeuwen, F.; van Genderen, A. M.
We present an interpretation of Hipparcos Hp and Walraven VBLUW photometry of the brightest star in the open cluster NGC 2362 (although not necessarily associated with this cluster), HD 57061 (30tau CMa, HR 2782, HIP 35415). In this multiple system the central component consist of a visual double star, two O-type stars separated by 0\farcs 151, wh…
Zero-metallicity very low mass stars as halo dark matter.
Kerins, E. J.
Hubble Space Telescope (HST) limits on the amount of halo dark matter (DM) in the form of very low-mass (VLM) stars close to the hydrogen-burning limit have been interpreted as excluding such stars as viable candidates. However, these limits assume that the stars are smoothly distributed and have at least the metallicity of Population II stars, wh…
Ultraviolet Spectral Morphology of the Stellar Core of eta Carinae
Walborn, Nolan R.; Ebbets, Dennis C.; Parker, Joel Wm.
We present high-quality spectra of eta Car between 1203 and 1765 A obtained with the Goddard High Resolution Spectrograph on board the Hubble Space Telescope. A square entrance slit 0."22 in diameter was used to isolate the brightest region of the core, "component A," from the nearby knots of ejecta and the nebulosity in which it is embedded. The …
Sounding the Sun's Chromosphere
Duvall, T. L., Jr.; Shibahashi, H.; Jefferies, S. M. +3 more
Time-distance analysis of solar acoustic waves with frequencies above the nominal atmospheric acoustic cutoff frequency (~5.3 mHz) shows partial reflection of the waves at both the Sun's photosphere and a layer located higher in the atmosphere. This result supports recent reports of chromospheric modes.
Atomic Data for the Re II UV 1 Multiplet and the Rhenium Abundance in the HgMn-type Star χ Lupi
Wahlgren, Glenn M.; Lawler, J. E.; Leckrone, David S. +5 more
We report new laboratory spectroscopic analyses that have been conducted to acquire wavelength and oscillator strength data for lines of the Re II UV 1 multiplet. Wavelengths were determined to a sub-milliangstrom accuracy for the hyperfine and isotopic structure components from laboratory spectra obtained with the Lund VUV Fourier Transform Spect…
HIPPARCOS parallaxes and the nature of δ Scuti stars.
Hog, E.; Petersen, J. O.
Hipparcos parallaxes give new tests of the nature of δ Sct variables. For many individual stars accurate distances are now available, i.e. directly determined luminosities and radii can be used to test theoretical models. Of particular interest are the at present very unclear relations between high-amplitude δ Sct stars and the much more abundant …
Lyα-induced Fluorescence of H2 and Co in Hubble Space Telescope Spectra of a Comet Shoemaker-Levy 9 Impact Site on Jupiter
Wolven, Brian C.; Feldman, Paul D.; Strobel, Darrell F. +1 more
Far-ultraviolet spectra of Jupiter obtained on 1994 July 20 in the region of the Shoemaker-Levy 9 G-fragment impact site contain features that differ markedly from the typical Jovian dayglow spectrum. These features are identified as fluorescence of H2 due to pumping by solar Lyα photons, which requires the presence of a substantial pop…
Correlated X-ray spectral and fast-timing behaviour of 4U 1636-53.
van der Klis, M.; Prins, S.
We present a study of the persistent X-ray emission from the low-mass X-ray binary 4U 1636-53 based on the entire archival EXOSAT ME data set. We performed a homogeneous analysis of all five EXOSAT observations in terms of the correlated rapid X-ray variability and X-ray spectral properties by means of power spectra, and colour-colour and hardness…
Infrared Observations Of Volatile Molecules In Comet Hale-Bopp
Crovisier, J.
Infrared observations of comets C/1996 B2 (Hyakutake) and C/1995 O1 (Hale-Bopp) benefited from the high spectral resolution and sensitivity of échelle spectrometers now equipping ground-based telescopes and from the availability of the Infrared Space Observatory (ISO). From the ground, several hydrocarbons were unambiguously detected for the first…
Temperatures and Altitudes of Jupiter's Ultraviolet Aurora Inferred from GHRS Observations with the Hubble Space Telescope
Fox, J. L.; Caldwell, John J.; Kim, Y. H.
We observed the jovian UV auroral regions with the Goddard high resolution spectrograph (GHRS) on board the Hubble Space Telescope (HST) on Apr. 29, May 2, and June 10, 1995. Observations of target areas were made in pairs in the two wavelength ranges 1257-1293 Å and 1587-1621 Å. Spectra in the long wavelength range are dominated by emissions of t…