Search Publications
The Problem of HIPPARCOS Distances to Open Clusters. I. Constraints from Multicolor Main-Sequence Fitting
Pinsonneault, Marc H.; Stauffer, John; Soderblom, David R. +2 more
Parallax data from the Hipparcos mission allow the direct distance to open clusters to be compared with the distance inferred from main-sequence (MS) fitting. There are surprising differences between the two distance measurements, indicating either the need for changes in the cluster compositions or reddening, underlying problems with the techniqu…
Optical-Infrared Spectral Energy Distributions of Z > 2 Lyman Break Galaxies
Sawicki, Marcin; Yee, H. K. C.
Broadband optical and IR spectral energy distributions are determined for spectroscopically confirmed z > 2 Lyman break objects in the Hubble Deep Field (HDF). These photometric data are compared with spectral synthesis models which take into account the effects of metallicity and of internal reddening due to dust. It is found that, on average,…
X-ray flare sparks quake inside Sun
Kosovichev, A. G.; Zharkova, V. V.
Solar flares involve a release of the Sun's magnetic energy as X-radiation, particle beams and high-speed plasma flows. But we have discovered, using data from the Solar and Heliospheric Observatory (SOHO), that these flares also affect the Sun's interior, generating seismic waves similar to earthquakes. For example, a three-kilometre-high seismic…
Carbon Stars
Knapp, Gillian R.; Wallerstein, George
Absolute magnitudes are estimated for carbon stars of various subtypes in the Hipparcos catalogue and as found in the Magellanic Clouds. Stellar radii fall within the limits of 2.4-4.7 AU. The chemical composition of carbon stars indicates that the C-N stars show nearly solar C/H, N/H, and ^12C/^13C ratios. This indicates that much of the C and N …
HST/WFPC2 Observations of Warm Ultraluminous Infrared Galaxies
Sanders, D. B.; Veilleux, Sylvain; Mazzarella, J. M. +2 more
We present new high-resolution B- and I-band images of a nearly complete sample of nine ``warm'' (f25/f60 > 0.2), ultraluminous infrared galaxies (ULIGs) obtained with the Wide Field Planetary Camera of the Hubble Space Telescope (HST). The HST images clearly reveal the presence of tidal tails and other features associated…
The Luminosity Function and Initial Mass Function in the Galactic Bulge
Grillmair, Carl J.; Holtzman, Jon A.; Lynds, Roger +5 more
We present deep photometry obtained with the Hubble Space Telescope in a field in Baade's window in the Galactic bulge. We derive a luminosity function down to I ~ 24.3, or V ~ 27.5, corresponding to M ~ 0.3 M_⊙. The luminosity function from the turnoff down to this level appears remarkably similar to that observed in the solar neighborhood. We de…
Hubble Space Telescope and VLA Observations of Seyfert 2 Galaxies: The Relationship between Radio Ejecta and the Narrow-Line Region
Simpson, Chris; Wilson, Andrew S.; Falcke, Heino
We present HST/WFPC2 images, in narrowband filters containing the [O III] λ5007 and Hα + [N II] emission lines and their adjacent continua, of a sample of seven Seyfert 2 galaxies selected because they possess either extended emission-line regions in ground-based observations or a hidden broad-line region in polarized light. Six of the galaxies ha…
Abundances of Deuterium and Helium-3 in the Protosolar Cloud
Geiss, J.; Gloeckler, G.
The mass spectrometric determinations of the isotopic composition of helium in the solar wind obtained from (1) the Apollo Solar Wind Composition (SWC) experiment, (2) the Ion Composition Instrument (ICI) on the International Sun Earth Explorer 3 (ISEE-3), and (3) the Solar Wind Composition Spectrometer (SWICS) on Ulysses are reviewed and discusse…
Imaging of the EGG Nebula (CRL 2688) with WFPC2/HST: A History of AGB/Post--AGB Giant Branch Mass Loss
Holtzman, J. A.; Gallagher, J. S., III; Clarke, J. T. +14 more
The proto-planetary nebula, CRL 2688, has been imaged through a wideband filter centered at 606 nm (F606W) with the Wide Field Planetary Camera 2 onboard the Hubble Space Telescope. CRL 2688 is the prototypical bipolar reflection nebula in which a star is surrounded by a dense, flattened cocoon of dust seen nearly edge-on and starlight escapes pre…
Spatial structure of the solar wind and comparisons with solar data and models
Hoeksema, J. T.; Galvin, A. B.; Steinberg, J. T. +10 more
Data obtained by instruments on the Ulysses spacecraft during its rapid sweep through >90° of solar latitude, crossing the solar equator in early 1995, were combined with data obtained near Earth by the Wind spacecraft to study the spatial structure of the solar wind and to compare to different models of the interplanetary magnetic field derive…