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Lyman-Alpha Absorption and the D/H Ratio in the Local Interstellar Medium
Vidal-Madjar, A.; Audouze, J.; Landsman, W. +5 more
Using the Goddard High Resolution Spectrograph onboard the Hubble Space Telescope, we have observed Lyα absorption against stellar chromospheres along six lines of sight, with additional observations of the Mg II H and K lines along five of the lines of sight and Fe II absorption along four of the lines of sight. We found absorption near the proje…
HST and Merlin Observations of 3C 264--A Laboratory for Jet Physics and Unified Schemes
Baum, Stefi A.; O'Dea, Christopher P.; Sparks, William B. +10 more
We present new HST optical continuum and emission line WFPC2 images and MERLIN radio observations of 3C 264 at ~0.1" resolution. The jet is well resolved in both the optical and radio images. In addition, we report the discovery of an apparent optical ``ring'' at a projected radius of ~300-400 pc. The ring is most likely the manifestation of absor…
A New Measurement of the Electron Density in the Local Interstellar Medium
Wood, Brian E.; Linsky, Jeffrey L.
Using the echelle-A grating of the Goddard High-Resolution Spectrograph, we have observed the C II λλ1335, 1336 emission lines of the nearby (d = 13.3 pc) star system Capella (G8 III + G1 III). Interstellar C II absorption features are detected within both stellar emission lines. The ground-state and excited-state C II column densities derived fro…
Hubble Space Telescope Imaging of z >= 0.4 Quasar Host Galaxies Selected by Quasar Radio and Optical Properties
Foltz, Craig B.; Hooper, Eric J.; Impey, Chris D.
A sample of 16 quasars selected from the Large Bright Quasar Survey in the redshift range 0.4 < z < 0.5 has been imaged in the R band with the Planetary Camera on the WFPC2 instrument of the Hubble Space Telescope. The host galaxy magnitudes are mostly similar to or brighter than L*, and the host luminosity is positively correlated with the …
Multiwavelength Observations of 3C 273 in 1993-1995
McHardy, I.; Ghisellini, G.; McBreen, B. +30 more
We present the results of the multiwavelength campaigns on 3C 273 in 1993-1995. During the observations in late 1993, this quasar showed an increase of its flux for energies >=100 MeV from about 2.1 × 10-7 photons cm-2 s-1 to approximately 5.6 × 10-7 photons cm-2 s-1 during a rad…
Solar Wind Stream Interactions and the Wind Speed-Expansion Factor Relationship.
Goldstein, B. E.; Phillips, J. L.; Sheeley, N. R., Jr. +1 more
Previous studies have shown that the solar wind speed observed near Earth is inversely correlated with the divergence rate of magnetic flux tubes near the Sun. We test the global validity of this relationship by employing Ulysses wind speed measurements during 1990-1997 as well as inecliptic data for 1976-1997. When the correspondence between wind…
A two-dimensional simulation of the radial and latitudinal evolution of a solar wind disturbance driven by a fast, high-pressure coronal mass ejection
Riley, Pete; Gosling, J. T.; Pizzo, V. J.
Using a hydrodynamic simulation, we have studied the two-dimensional (symmetry in the azimuthal direction) evolution of a fast, high-pressure coronal mass ejection (CME) ejected into a solar wind with latitudinal variations similar to those observed by Ulysses. Specifically, the latitudinal structure of the ambient solar wind in the meridional pla…
Hubble Space Telescope WFPC2 Observations of the Binary Fraction among Pre-Main-Sequence Cluster Stars in Orion
Strom, Stephen E.; Padgett, Deborah L.; Ghez, Andrea
We present estimates of the binary frequency for optically visible (IHST < 19 mag) members of the dense (mean star separation ~0.05 pc) embedded stellar clusters associated with NGC 2024, NGC 2068, and NGC 2071 (distance = 460 pc) based on Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) observations. Of 99 targets,…
Adaptive Optics 0.2" Resolution Infrared Images of HL Tauri: Direct Images of an Active Accretion Disk around a Protostar
Roddier, Claude; Close, Laird M.; Roddier, François +2 more
We have obtained 0.2" FWHM images of HL Tau at K', H, and J utilizing the University of Hawaii Adaptive Optics System at the 3.6 m CFHT. These are the highest resolution deep images of HL Tau ever obtained in the infrared. They provide unique insight into HL Tau's circumstellar environment. An active accretion disk is directly resolved around HL T…
Dynamical Correlations for Globular Clusters in M31,
Djorgovski, S. G.; McCarthy, J. K.; Meylan, G. +5 more
We present internal velocity dispersion measurements for a set of 21 globular clusters in the Andromeda galaxy (M31). We combine them with structural and photometric cluster parameters measured earlier with the Hubble Space Telescope and from the ground to explore correlations of cluster properties and to compare them with the equivalent correlati…