Search Publications
HD 98800: A Unique Stellar System of Post-T Tauri Stars
Torres, Guillermo; Latham, David W.; Henry, Todd J. +15 more
HD 98800 is a system of four stars, and it has a large infrared excess that is thought to be due to a dust disk within the system. In this paper we present new astrometric observations made with Hipparcos, as well as photometry from Hubble Space Telescope WFPC2 images. Combining these observations and reanalyzing previous work allow us to estimate…
Flows and Horizontal Displacements from Ring Diagrams
Schou, J.; Bogart, R. S.
A new algorithm for analyzing ring diagrams from helioseismic data is presented. This method is applied to two months of Solar and Heliospheric Observatory/Michelson Doppler Imager data from 1996 May 24 through July 24 to study flows and to measure the ratio of the horizontal displacement to the vertical displacement for the oscillations. We find …
Infrared Space Observatory Long Wavelength Spectrometer Observations of a Cold Giant Molecular Cloud Core near the Galactic Center
Menten, Karl M.; Lis, D. C.
We have used the Long Wavelength Spectrometer aboard the Infrared Space Observatory in the grating mode to map the far-infrared continuum emission (45-175 µm) toward the massive giant molecular cloud core GCM 0.25+0.11 located near the Galactic center. Graybody models of the observed far-infrared spectral energy distribution indicate that th…
Oscillation mode identifications and models for the delta Scuti star FG Virginis
Kjeldsen, H.; Bruntt, H.; Frandsen, S. +4 more
We present new spectroscopic and photometric time series observations of the delta Scuti star FG Vir. We detect the oscillations via changes in the equivalent widths of hydrogen and metal absorption lines. From the ratios between spectroscopic and photometric amplitudes, we assign l values to the eight strongest oscillation modes. In particular, w…
Wolf-Rayet stars and O-star runaways with HIPPARCOS. II. Photometry
van der Hucht, K. A.; Moffat, A. F. J.; van den Heuvel, E. P. J. +9 more
Abundant {HIPPARCOS photometry over 3 years of 141 O and Wolf-Rayet stars, including 8 massive X-ray binaries, provides a magnificent variety of light curves at the sigma ~ 1-5% level. Among the most interesting results, we mention: optical outbursts in HD 102567 (MXRB), coinciding with periastron passages; drastic changes in the light curve shape…
Detection of spatial variations in the (D/H) ratio in the local interstellar medium
Vidal-Madjar, Alfred; Koester, Detlev; Ferlet, Roger +6 more
We present high resolution (Delta lambda = 3.7 km.s^{-1}) HST-GHRS observations of the DA white dwarf G191-B2B, and derive the interstellar D/H ratio on the line of sight. We have observed and analysed simultaneously the interstellar lines of Hi, D i, N i, O i, Si ii and Si iii. We detect three absorbing clouds, and derive a total Hi\ column densi…
Galactic Interior Motions Derived from HIPPARCOS Proper Motions. I. Young Disk Population
Zhu, Zi; Miyamoto, Masanori
Analyzing Hipparcos proper motions of 1352 O-B5 stars other than the Gould belt stars, which are representative of the young disk population, we have found a clear stellar warping motion that is a systematic rotation +3.8 +/- 1.1 km s^-1 kpc^-1 of stars about the axis pointing to the Galactic center in the sense of increasing the inclination of th…
The edge-on spiral gravitational lens B1600+434
Koopmans, L. V. E.; Jackson, N.; de Bruyn, A. G.
We present new observations of the gravitational lens (GL) system B1600+434, strongly suggesting that the lens is an edge-on spiral galaxy. These observations are used to constrain the mass model of the system, in particular the oblateness and velocity dispersion of the dark matter halo around the lensing galaxy. From an analytical model we find a…
Jet-induced Shocks in 3C 171: An Intermediate-Redshift Analog of High-Redshift Radio Galaxies
Tadhunter, C. N.; Axon, D. J.; Robinson, A. +2 more
We present spectroscopic observations of the extended emission-line region (EELR) aligned with the radio axis of the powerful radio galaxy 3C 171. The results obtained from a detailed analysis of the observational data show that shocks induced by jet-cloud interactions have a dramatic effect on the extended line-emitting gas. The evidence for shoc…
Evidence for water ice and estimate of dust production rate in comet Hale-Bopp at 2.9 AU from the Sun
Altieri, B.; Keller, H. U.; Lellouch, E. +7 more
We report observational evidence for water ice in comet C/1995 O1 (Hale-Bopp) when it was at 2.9 AU from the Sun, from emission features at 44 and 65 mu m, and possibly an absorption feature at 3.1 mu m, observed with ISO/LWS and PHT. We find that icy grains have mean radii of 15 mu m within a factor of 2, lifetimes of ~ 2 days, a temperature of ~…