Search Publications
A Statistical Study of Multiply Imaged Systems in the Lensing Cluster Abell 68
Richard, Johan; Ellis, Richard; Kneib, Jean-Paul +8 more
We have carried out an extensive spectroscopic survey with the Keck and VLT telescopes, targeting lensed galaxies in the background of the massive cluster Abell 68. Spectroscopic measurements are obtained for 26 lensed images, including a distant galaxy at z=5.4. Redshifts have been determined for 5 out of 7 multiple-image systems. Through a caref…
The Interaction between Radio Lobes and Hot Gas in the Nearby Radio Galaxies 3C 285 and 3C 442A
Hardcastle, M. J.; Croston, J. H.; Birkinshaw, M. +4 more
We present Chandra observations of two nearby radio galaxies in group environments, 3C 285 and 3C 442A. The host galaxies of both sources are involved in mergers with nearby massive galaxies, and the hot gas in the systems is extended along lines joining the interacting galaxies. Both sources show strong evidence for interactions between the radio…
Precision Masses of the Low-Mass Binary System GJ 623
Ireland, Michael J.; Martinache, Frantz; Lloyd, James P. +2 more
We have used aperture masking interferometry and adaptive optics (AO) at the Palomar 200 inch telescope to obtain precise mass measurements of the binary M dwarf GJ 623. AO observations spread over 3 yr combined with a decade of radial velocity measurements constrain all orbital parameters of the GJ 623 binary system accurately enough to criticall…
Neon and Oxygen Absolute Abundances in the Solar Corona
Landi, E.; Doschek, G. A.; Feldman, U.
In the present work we use the UV spectrum of a solar flare observed with SOHO SUMER to measure the absolute abundance of Ne in the solar atmosphere. The measurement is carried out using the intensity ratio between the allowed 1s2s3S1-1s2p3P2 Ne IX line at 1248.28 Å and the free-free continuum radiation …
A Spectroscopic Study of Field and Runaway OB Stars
Gies, Douglas R.; Boyajian, Tabetha S.; Grundstrom, Erika D. +1 more
Identifying binaries among runaway O- and B-type stars offers valuable insight into the evolution of open clusters and close binary stars. Here we present a spectroscopic investigation of 12 known or suspected binaries among field and runaway OB stars. We find new orbital solutions for five single-lined spectroscopic binaries (HD 1976, HD 14633, H…
Unveiling the Core of the Globular Cluster M15 in the Ultraviolet
Knigge, C.; Charles, P. A.; Long, K. S. +4 more
We have obtained deep FUV and NUV images of the inner region of the dense globular cluster M15 with the HST ACS. The FUV-NUV color-magnitude diagram shows a well-defined track of horizontal branch stars, as well as a trail of blue stragglers and white dwarfs. The main-sequence turnoff is clearly visible at FUV~=23.5 mag and FUV-NUV~=3 mag, and the…
Are All Coronal Mass Ejections Hollow Flux Ropes?
Krall, J.
A quantitative specification of a three-dimensional flux rope is examined statistically for comparison to previously published statistical measures of coronal mass ejections (CMEs) as observed by the Solar Maximum Mission (SMM) spacecraft. The three-dimensional geometry that has been previously shown to reproduce statistical measures (average angu…
The Posteruptive Evolution of a Coronal Dimming
McIntosh, Scott W.; Davey, Alisdair R.; Leamon, Robert J. +1 more
We discuss the posteruptive evolution of a ``coronal dimming'' based on observations of the EUV corona from the Solar and Heliospheric Observatory and the Transition Region and Coronal Explorer (TRACE). This discussion highlights the roles played by magnetoconvection-driven magnetic reconnection and the global magnetic environment of the plasma in…
Seismic Study of the Chemical Composition of the Solar Convection Zone
Basu, Sarbani; Antia, H. M.; Lin, Chia-Hsien
Recent downward revision of solar heavy-element abundances using a three-dimensional atmospheric model has introduced serious discrepancies between standard solar models and helioseismic inferences about solar structure. In this paper we investigate the possibility of determining the heavy-element abundances using helioseismic inversion techniques…
Contamination by Surface Effects of Time-Distance Helioseismic Inversions for Sound Speed beneath Sunspots
Rajaguru, S. P.; Couvidat, S.
Using Doppler velocity data from the SOI/MDI instrument on board the SOHO spacecraft, we do time-distance helioseismic inversions for sound-speed perturbations beneath 16 sunspots observed in high-resolution mode. We clearly detect ringlike regions of enhanced sound speed beneath most sunspot penumbrae, extending from near the surface to depths of…