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Acoustic Power Maps of Solar Active Regions
Brown, Timothy M.; Hindman, Bradley W.
Using observations made by the Michelson Doppler Imager (MDI), we find that within solar active regions the spatial distributions of Doppler velocity power and continuum intensity power differ. The oscillation power within any pixel is a strong function of the magnetic field strength within that pixel. The amplitudes of oscillations with frequenci…
Spatially Resolved Hubble Space Telescope Spectra of the Chromosphere of alpha Orionis
Dupree, A. K.; Gilliland, R. L.; Uitenbroek, H.
Spatially resolved UV spectra of the supergiant alpha Orionis (Betelgeuse) obtained in 1995 March with the Goddard High Resolution Spectrograph (GHRS) on board the Hubble Space Telescope (HST) show that the chromospheric emission in the Mg II h and k (around 280 nm) lines reaches a diameter of at least ~270 milliarcseconds, about twice the size of…
Hubble Space Telescope observations of the nucleus and inner coma of comet 19P/1904 Y2 (Borrelly)
Weaver, Harold A.; Toth, Imre; Lamy, Philippe L.
The nucleus of comet 19P/Borrelly was detected using the Planetary Camera (WFPC2) of the Hubble Space Telescope (HST). During the time of our observations, the comet was 0.62 AU from the Earth, 1.40 AU from the Sun, and had a solar phase angle of 38°. The high spatial resolution of the HST images allowed us to discriminate clearly between the sign…
Mass Segregation in Young Large Magellanic Cloud Clusters. I. NGC 2157
Mateo, Mario; Pryor, Carlton; Fischer, Philippe +2 more
We have carried out Wide Field Planetary Camera 2 V- and I-band imaging of the young LMC cluster NGC 2157. Construction of a color-magnitude diagram and isochrone fitting yield an age of tau = 10^8 yr, a reddening E(B - V) = 0.1, and a distance modulus of 18.4 mag. Our data cover the mass range 0.75 M_⊙ <= m <= 5.1 M_⊙. We find that the clus…
Star Formation in and Evolution of the Blue Compact Dwarf Galaxy UGC 6456 Determined from Hubble Space Telescope Images
Tolstoy, Eline; Lynds, Roger; O'Neil, Earl J., Jr. +1 more
Photometry on the UVI system has been performed on the resolved stellar content of the blue compact dwarf galaxy UGC 6456 using Wide Field Planetary Camera 2 (WFPC2) images obtained with the Hubble Space Telescope. The resulting color-magnitude diagram (CMD) goes to about V = 27.5 and reveals not only a young population of blue main-sequence stars…
Mid-IR emission of galaxies in the Virgo cluster. II. Integrated properties
Boulanger, F.; Sauvage, M.; Boselli, A. +7 more
We analyse the integrated properties of the Mid-IR emission of a complete, optically selected sample of galaxies in the Virgo cluster observed with the ISOCAM instrument on board the ISO satellite. The ISOCAM data allows us to construct the luminosity distribution at 6.75 and 15 mu m of galaxies for different morphological classes. These data are …
A ``Short'' Distance to the Large Magellanic Cloud With the Hipparcos Calibrated Red Clump Stars
Zaritsky, D.; Stanek, K. Z.; Harris, J.
Following an approach developed by Paczyński & Stanek, we derive a distance to the Large Magellanic Cloud (LMC) by comparing red clump stars from the Hipparcos catalog with the red clump stars observed in two fields in the LMC that were selected from the ongoing photometric survey of the Magellanic Clouds to lie in low-extinction regions. The …
The distribution of nearby stars in phase space mapped by HIPPARCOS. II. Inhomogeneities among A-F type stars
Creze, M.; Chereul, E.; Bienayme, O.
A volume limited and absolute magnitude limited sample of A-F type dwarfs within 125 parsecs of the Sun is searched for inhomogeneities in the density-velocity space, expecting signatures of the cluster evaporation, phase mixing and possible disc heating mechanisms. A 3-D wavelet analysis is used to extract inhomogeneities, both in the density and…
Characteristics of the Galileo probe entry site from Earth-based remote sensing observations
Baines, Kevin H.; Hora, Joseph; Hinkley, Sasha +14 more
A reassessment of ground-based observations confirms to better than a 98% confidence level that the Galileo probe entered a 5-µm hot spot, a region of unusual clarity and dryness, some 900+/-300km north of its southern boundary. Cloud conditions at that point were similar to those in the center of this region, some 600 km further north. At t…
A High-Dispersion Spectroscopic Survey of the Hot White Dwarfs: The IUE NEWSIPS SWP Echelle Data Set
Barstow, M. A.; Sion, E. M.; Holberg, J. B.
This paper summarizes the results obtained from a comprehensive analysis of all of the SWP echelle spectra of the white dwarf stars contained in the IUE Final Archive. A total of 209 NEWSIPS spectra of 55 degenerate stars of various types have been systematically reduced and analyzed. These include, in addition to conventional white dwarfs, severa…