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The First Direct Measurement of the Mass of a Blue Straggler in the Core of a Globular Cluster: BSS 19 in 47 Tucanae
Livio, Mario; Saffer, Rex A.; Shara, Michael M.
Hot, young blue straggler stars are observed by the Hubble Space Telescope to exist in the cores of very old globular clusters. Theory maintains that these stars must be more massive than hydrogen-burning cluster members that are as old as the clusters themselves. We have, for the first time, verified this theoretical claim by directly measuring t…
Hubble Space Telescope Observations of the Blue Compact Dwarf SBS 0335-052: A Probable Young Galaxy
Thuan, Trinh X.; Izotov, Yuri I.; Lipovetsky, Valentin A.
We present HST WFPC2 V and I images and GHRS UV spectrophotometry of the spectral regions around Lyα and O I λ1302 of the extremely metal-deficient (Z ~ Z⊙/41) blue compact dwarf galaxy (BCD) SBS 0335-052. All the star formation in the BCD occurs in six super-star clusters (SSCs) with ages <=25 Myr, within a region of ~2" or 520 pc i…
Carbon in the Diffuse Interstellar Medium
Sofia, Ulysses J.; Meyer, David M.; Cardelli, Jason A. +1 more
We have obtained spectra of the interstellar intersystem C II] λ2325 line toward the star τ Canis Majoris. The absorption spectra were obtained with the echelle mode (3.5 km s-1 resolution) of the Goddard High Resolution Spectrograph aboard the Hubble Space Telescope and have a co-added signal-to-noise ratio of approximately 850. The C …
Composition of Interstellar Clouds in the Disk and Halo. IV. HD 215733
Fitzpatrick, Edward L.; Spitzer, Lyman, Jr.
In this paper we continue our investigation of diffuse clouds in the interstellar medium with an analysis of the line of sight toward the star HD 215733, located in the Galactic halo some 1700 pc below the plane. As in our previous papers, we utilize the component-fitting technique to determine velocities, velocity widths, and column densities for…
Discovery of Interstellar Hydrogen Fluoride 1
Neufeld, David A.; Phillips, Thomas G.; Schilke, Peter +1 more
We report the first detection of interstellar hydrogen fluoride. Using the Long Wavelength Spectrometer of the Infrared Space Observatory (ISO), we have detected the 121.6973 µm J=2-1 line of HF in absorption toward the far-infrared continuum source Sagittarius B2. The detection is statistically significant at the 13 σ level. On the basis of…
The Evolution of Galactic Boron and the Production Site of the Light Elements
Deliyannis, Constantine P.; Primas, F.; Rebull, L. M. +5 more
The Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) has been used to obtain spectra of the 2500 Å region in eight stars with metallicities ranging from [Fe/H] = -0.4 to -3.0, including the most metal-poor star ever observed for boron. Spectrum synthesis utilizing latest Kurucz model atmospheres has been used to dete…
High Spatial Resolution Imaging of Pre-Main-Sequence Binary Stars: Resolving the Relationship between Disks and Close Companions
Ghez, A. M.; White, Russel J.; Simon, M.
In order to study the passive and active effects of young close companion stars and to constrain possible multiple star formation mechanisms, we have carried out a high-resolution imaging program of six multiple T Tauri star systems using the Hubble Space Telescope from 0.3 to 0.9 µm and ground-based speckle imaging from 1 to 2 µm. Eac…
Determining the Hubble Constant from the Gravitational Lens PG 1115+080
Keeton, C. R.; Kochanek, C. S.
For the quadruple gravitational lens PG 1115+080, we combine recent measurements of the time delays with new lens models to determine the Hubble constant H0. We explore the effects of systematic uncertainties in the lens models on the estimates of H0, and we discuss how the uncertainties can be reduced by future observations.…
Cepheid Calibration of the Peak Brightness of Type Ia Supernovae. VIII. SN 1990N in NGC 4639
Panagia, N.; Saha, A.; Labhardt, Lukas +3 more
Repeated imaging observations have been made of NGC 4639 with the Hubble Space Telescope between 1995 April and July over an interval of 71 days. Images were obtained on 12 epochs in the F555W band and on two epochs in the F814W band. The galaxy is parent to the prototypical Type Ia supernova SN 1990N. A total of 18 definite and six likely Cepheid…
Origins of the Slow and the Ubiquitous Fast Solar Wind
Fineschi, S.; O'Neal, R.; Kohl, J. +4 more
We present in this Letter the first coordinated radio occultation measurements and ultraviolet observations of the inner corona below 5.5Rs, obtained during the Galileo solar conjunction in 1997 January, to establish the origin of the slow solar wind. Limits on the flow speed are derived from the Doppler dimming of the resonantly scatte…