Search Publications
Ten Low-Mass Companions from the Keck Precision Velocity Survey
Butler, R. Paul; Vogt, Steven S.; Fischer, Debra A. +4 more
Ten new companions have emerged from the Keck precision Doppler velocity survey, with minimum (Msini) masses ranging from 0.8 MJUP to 0.34 Msolar. Five of these are planet candidates with Msini<12 MJUP, two are brown dwarf candidates with Msini~30 MJUP, and three are low-mass stellar companions. Hippa…
Magnetic Topology of Impulsive and Gradual Solar Energetic Particle Events
Reames, Donald V.
We examine the magnetic topology at the Sun that leads to the two classes of impulsive and gradual solar energetic particle (SEP) events so as to address new observations that seem to blur this classification, for example, that coronal mass ejections (CMEs) can accompany events of both classes. In our model, the unusual element abundances in impul…
The Star Formation History of the Large Magellanic Cloud
Cole, Andrew A.; Gallagher, John S., III; Stetson, Peter B. +1 more
Using WFPC2 on board the Hubble Space Telescope, we have created deep color-magnitude diagrams in the V and I passbands for approximately 105 stars in a field at the center of the LMC bar and another in the disk. The main-sequence luminosity functions (LFs) from 19<=V<=23.5, the red clump and horizontal branch morphologies, and th…
Intracluster Red Giant Stars in the Virgo Cluster
Ciardullo, Robin; Sigurdsson, Steinn; Durrell, Patrick R. +2 more
We have used the Wide Field Planetary Camera 2 on the Hubble Space Telescope to obtain deep F814W images of a blank field in the Virgo Cluster located 41' northwest of M87. We perform star counts in that field and in another Virgo field observed by Ferguson, Tanvir, & von Hippel and show that when compared to the Hubble Deep Field-North and Hu…
The Structure and Evolution of a Sigmoidal Active Region
Liu, Y.; Mason, H. E.; Thompson, B. J. +13 more
Solar coronal sigmoidal active regions have been shown to be precursors to some coronal mass ejections. Sigmoids, or S-shaped structures, may be indicators of twisted or helical magnetic structures, having an increased likelihood of eruption. We present here an analysis of a sigmoidal region's three-dimensional structure and how it evolves in rela…
Spectral Evidence for Widespread Galaxy Outflows at z > 4
Broadhurst, Tom; Frye, Brenda; Benítez, Narciso
We present discovery spectra of a sample of eight lensed galaxies at high redshift, 3.7<z<5.2, selected by their red colors in the fields of four massive clusters: A1689, A2219, A2390, and AC 114. Metal absorption lines are detected and observed to be blueshifted by 300-800 km s-1 with respect to the centroid of Lyα emission. A co…
Hubble Space Telescope Space Telescope Imaging Spectrograph Observations of the Bipolar Jet from RW Aurigae: Tracing Outflow Asymmetries Close to the Source
Bacciotti, Francesca; Eislöffel, Jochen; Davis, Christopher J. +2 more
We have observed the bipolar jet from RW Aur A with STIS on board the Hubble Space Telescope. After continuum subtraction, morphological and kinematic properties of this outflow can be traced to within 0.1" from the source in forbidden emission lines. The jet appears well collimated, with typical FWHMs of 20-30 AU in the first 2" and, surprisingly…
The Population of Weak Mg II Absorbers. II. The Properties of Single-Cloud Systems
Charlton, Jane C.; Churchill, Christopher W.; Rigby, Jane R.
We present an investigation of Mg II absorbers characterized as single-cloud ``weak systems'' [defined by Wr(λ2796)<0.3 Å] at z~1. We measured column densities and Doppler parameters for Mg II and Fe II in 15 systems found in High Resolution Echelle Spectrometer/Keck spectra at 6.6 km s-1. Using these quantities and C IV, …
Composition of Anomalous Cosmic Rays and Other Heliospheric Ions
Cummings, A. C.; Stone, E. C.; Steenberg, C. D.
Interstellar pickup ions accelerated by the termination shock of the solar wind dominate the anomalous cosmic-ray (ACR) intensities observed by the Voyager spacecraft in the outer heliosphere. Using a two-dimensional acceleration and propagation model, we derive the relative abundances of these interstellar ACRs and determine the mass dependence o…
Infrared Views of the TW Hydra Disk
Zuckerman, B.; Schneider, G.; Hines, D. C. +6 more
The face-on disk around TW Hya is imaged in scattered light at 1.1 and 1.6 µm using the coronagraph in the Near Infrared Camera and Multi Object Spectrometer aboard the Hubble Space Telescope. Stellar light scattered from the optically thick dust disk is seen from 20 to 230 AU. The surface brightness declines as a power law of r-2.6+/-0…