Search Publications
Size and Structure of the Narrow-Line Region of Quasars
Wilson, Andrew S.; Wills, Beverley J.; Falcke, Heino +2 more
We have observed the narrow-line regions (NLRs) of the seven brightest radio-quiet Palomar-Green (or Bright Quasar Survey) quasars (z<0.5) with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST). Linear-ramp filters were used to image the [O III] λ5007 line emission with 0.0455"-0.1" pixel resolution. We find that the N…
A statistical study on the geoeffectiveness of Earth-directed coronal mass ejections from March 1997 to December 2000
Wang, S.; Wang, J. X.; Wang, Y. M. +2 more
We have identified 132 Earth-directed coronal mass ejections (CMEs) based on the observations of the Large Angle Spectroscopic Coronagraph (LASCO) and Extreme Ultraviolet Imaging Telescope (EIT) on board of Solar and Heliospheric Observatory (SOHO) from March 1997 to December 2000 and carried out a statistical study on their geoeffectiveness. The …
The Halo Stars in NGC 5128. III. An Inner Halo Field and the Metallicity Distribution
Harris, William E.; Harris, Gretchen L. H.
We present new Hubble Space Telescope WFPC2 (V,I) photometry for field stars in NGC 5128 at a projected distance of 8 kpc from the galaxy center, which probes a mixture of its inner halo and outer bulge. The color-magnitude diagram shows an old red giant branch that is even broader in color than our two previously studied outer halo fields (at 21 …
The Axisymmetric Ejecta of Supernova 1987A
Panagia, N.; Lundqvist, P.; Fransson, C. +15 more
Extensive early observations proved that the ejecta of supernova 1987A (SN 1987A) are aspherical. The most important of these early observations include (1) the ``Bochum event'' that revealed small-scale spectroscopic structure indicating chemical inhomogeneities of the ejecta, (2) spectropolarimetry that showed deviations from spherical symmetry,…
Internal Dynamics, Structure, and Formation of Dwarf Elliptical Galaxies. I. A Keck/Hubble Space Telescope Study of Six Virgo Cluster Dwarf Galaxies
Geha, M.; van der Marel, R. P.; Guhathakurta, P.
Spectroscopy with the Keck II 10 m telescope and Echelle Spectrograph and Imager is presented for six Virgo Cluster dwarf elliptical (dE) galaxies in the absolute magnitude range -15.7<=MV<=-17.2. The mean line-of-sight velocity and velocity dispersion are resolved as a function of radius along the major axis of each galaxy, nearl…
Interaction of EIT Waves with Coronal Active Regions
Thompson, B. J.; Ofman, L.
Large-scale coronal waves associated with flares were first observed by the Solar and Heliospheric Observatory (SOHO) Extreme ultraviolet Imaging Telescope (EIT). We present the first three-dimensional MHD modeling of the interaction of the EIT waves with active regions and the possibility of destabilization of an active region by these waves. The…
Discovery of a Substellar Companion to the K2 III Giant ι Draconis
Butler, R. Paul; Fischer, Debra A.; Marcy, Geoffrey W. +3 more
We report precise radial velocity measurements of the K giant ι Dra (HD 137759, HR 5744, HIP 75458), carried out at Lick Observatory, which reveal the presence of a substellar companion orbiting the primary star. A Keplerian fit to the data yields an orbital period of about 536 days and an eccentricity of 0.70. Assuming a mass of 1.05 Msolar<…
The Magnetic Helicity Budget of a cme-Prolific Active Region
Mandrini, C. H.; Culhane, J. L.; Démoulin, P. +3 more
Coronal mass ejections (CMEs) are thought to be the way by which the solar corona expels accumulated magnetic helicity which is injected into the corona via several methods. DeVore (2000) suggests that a significant quantity is injected by the action of differential rotation, however Démoulin et al. (2002b), based on the study of a simple bipolar …
Global Far-Ultraviolet (912-1800 Å) Properties of Star-forming Galaxies
Heckman, Timothy M.; Calzetti, Daniela; Leitherer, Claus +1 more
We present the results of an archival study of the Hopkins Ultraviolet Telescope (HUT) Astro-2 database. Nineteen spectra of star-forming regions and starburst galaxies were retrieved, reprocessed, and analyzed. The spectra cover the wavelength region 912-1800 Å, providing access to the domain of peak luminosity from a young stellar population. We…
Gravitational Microlensing Events Due to Stellar-Mass Black Holes
Alcock, C.; Allsman, R. A.; Alves, D. R. +30 more
We present an analysis of the longest timescale microlensing events discovered by the MACHO Collaboration during a 7 year survey of the Galactic bulge. We find six events that exhibit very strong microlensing parallax signals due, in part, to accurate photometric data from the GMAN and MPS collaborations. The microlensing parallax fit parameters a…