Search Publications
The Three-Dimensional Ionization Structure and Evolution of NGC 6720, The Ring Nebula
O'Dell, C. R.; Henney, W. J.; Sabbadin, F.
We have determined the gas kinematics, diagnostic and ionic radial profiles, spatial structure, and evolutionary phase of NGC 6720 (the Ring Nebula) by means of tomography and a three-dimensional recovery technique applied to long-slit high-resolution spectra. The main shell of the Ring Nebula is a triaxial ellipsoid (radii of 0.10, 0.13, and 0.20…
Long-term atmospheric variability on Uranus and Neptune
Hammel, H. B.; Lockwood, G. W.
Long-term photometric measurements of Uranus and Neptune through 2005 show variations in brightness. For Uranus, much of the variation can be interpreted as seasonal, i.e., caused by viewing angle changes of an oblate planet. The photometry suggests that if seasonal variations on Uranus are north-south symmetric, then the northern pole should begi…
Spatial-Temporal characteristics of ion beamlets in the plasma sheet boundary layer of magnetotail
Grigorenko, Elena E.; Zelenyi, Lev M.; Sauvaud, Jean-Andre
The processes of nonadiabatic ion acceleration occurring in the vicinity of magnetic neutral lines produce highly accelerated (up to 2500 km/s) field-aligned ion beams (beamlets) with transient appearance streaming earthward in the plasma sheet boundary layer (PSBL) of the Earth's magnetotail. Previous studies of these phenomena based on single sp…
Diffuse gamma-ray emission from the Galactic center - a multiple energy injection model
Cheng, K. S.; Chernyshov, D. O.; Dogiel, V. A.
We suggest that the energy source of the observed diffuse gamma-ray emission from the direction of the Galactic center is the Galactic black hole Sgr A*, which becomes active when a star is captured at a rate of ~10-5 yr-1. Subsequently the star is tidally disrupted and its matter is accreted into the black hole. During the a…
Hydrogen Peroxide on Enceladus
Buratti, B. J.; Jaumann, R.; Momary, T. W. +2 more
Scientists have recently discovered a dynamic, geologically active world in Saturn's icy moon, Enceladus. This small satellite has a south polar hot spot at least 70 K hotter than surrounding regions and a plume of water vapor and ice particles surging from the ``tiger stripe'' cracks that flank the pole. Spectral data of the surface of Enceladus …
New Insights on Interstellar Gas-Phase Iron
Snow, Theodore P.; Jensen, Adam G.
In this paper we report on the gas-phase abundance of singly ionized iron (Fe II) for 51 lines of sight, using data from FUSE. Fe II column densities are derived by measuring the equivalent widths of several UV absorption lines and subsequently fitting those to a curve of growth. Our derivation of Fe II column densities and abundances creates the …
The Analysis of Penumbral Fine Structure Using an Advanced Inversion Technique
Tsuneta, Saku; Shimizu, Toshifumi; Ichimoto, Kiyoshi +8 more
We present a method to study the penumbral fine structure using data obtained by the spectropolarimeter on board Hinode. For the first time, the penumbral filaments can be considered as being resolved in spectropolarimetric measurements. This enables us to use inversion codes with only one-component model atmospheres, and thus to assign the obtain…
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…