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HST imaging of the globular clusters in the Fornax cluster: NGC1399 and NGC1404
Forbes, Duncan A.; Brodie, Jean P.; Grillmair, Carl J. +2 more
The Fornax cluster galaxies NGC1399 and NGC1404 are ideal for studying the effects of a cluster environment on globular cluster systems. Here we present new optical imaging of these two galaxies from both the Hubble Space Telescope's Wide Field and Planetary Camera 2 and the Cerro Tololo Inter-American Observatory 1.5-m telescope. The combination …
Two Jets from the Protostellar System L1551 IRS 5
Liseau, René; Fridlund, C. V. Malcolm
Hubble Space Telescope and ground-based observations of the jet emanating from the young stellar object L1551 IRS 5 clearly show a structure with two components, one of which terminates in a working surface only 1500 AU from the originating sources. This particular jet is found to be less dense than the ambient medium. Its Mach disk is found to be…
The Virgo Cluster Distance from 21 Centimeter Line Widths
Sandage, Allan; Tammann, G. A.; Federspiel, Martin
The distance of the Virgo cluster is derived in the B band from the 21 cm line width-absolute magnitude relation. This relation is calibrated using 18 spirals with Cepheid distances, mainly from the Hubble Space Telescope. The calibration is applied to a complete sample of nonpeculiar spirals with i > 45° lying within the optical (n = 49) or X-…
Color-Luminosity Relations for the Resolved Hot Stellar Populations in the Centers of M31 and M32
Ferguson, Henry C.; Brown, Thomas M.; Stanford, S. A. +1 more
We present Faint Object Camera (FOC) ultraviolet images of the central 14" × 14" of Messier 31 and Messier 32. The hot stellar populations detected in the composite UV spectra of these nearby galaxies are partially resolved into individual stars, and their individual colors and apparent magnitudes are measured. We detect 433 stars in M31 and 138 s…
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…