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The Absorption Spectrum of High-Density Stellar Ejecta in the Line of Sight to η Carinae
Gull, T. R.; Nielsen, K. E.; Bruhweiler, F. +3 more
Using the high-dispersion near-UV (NUV) mode of the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST) to observe η Carinae, we have resolved and identified over 500 sharp circumstellar absorption lines of iron-group singly ionized and neutral elements with ~20 velocity components ranging from -146 to -585 km s
A Dynamical Simulation of the Debris Disk around HD 141569A
Ford, H. C.; Infante, L.; Zheng, W. +36 more
We study the dynamical origin of the structures observed in the scattered-light images of the resolved debris disk around HD 141569A. The disk has two conspicuous spiral rings and two large-scale spiral arms. We explore the roles of radiation pressure from the central star, gas drag from the gas disk, and the tidal forces from two nearby stars in …
Intrinsic Absorption in the Spectrum of NGC 7469: Simultaneous Chandra, FUSE, and STIS Observations
Kaiser, Mary Elizabeth; Green, Richard F.; Scott, Jennifer E. +10 more
We present simultaneous X-ray, far-ultraviolet, and near-ultraviolet spectra of the Seyfert 1 galaxy NGC 7469 obtained with the Chandra X-Ray Observatory, the Far Ultraviolet Spectroscopic Explorer, and the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. Previous nonsimultaneous observations of this galaxy found two distinct UV…
A Comparison of Surface Brightness Profiles for Ultracompact Dwarfs and Dwarf Elliptical Nuclei: Implications for the ``Threshing'' Scenario
Drinkwater, M. J.; De Propris, R.; Jones, J. B. +4 more
Using imaging from the Hubble Space Telescope, we derive surface brightness profiles for ultracompact dwarfs in the Fornax Cluster and for the nuclei of dwarf elliptical galaxies in the Virgo Cluster. Ultracompact dwarfs are more extended and have higher surface brightnesses than typical dwarf nuclei, while the luminosities, colors, and sizes of t…
Characteristic Times of Gradual Solar Energetic Particle Events and Their Dependence on Associated Coronal Mass Ejection Properties
Kahler, S. W.
We use 20 MeV proton intensities from the EPACT instrument on Wind and coronal mass ejections (CMEs) from the LASCO coronagraph on SOHO observed during 1998-2002 to statistically determine three characteristic times of gradual solar energetic particle (SEP) events as functions of solar source longitude: (1) TO, the time from associated …
Luminosity Functions of the Galaxy Cluster MS 1054-0321 at z=0.83 based on ACS Photometry
Goto, Tomotsugu; Ford, H. C.; Demarco, R. +41 more
We present new measurements of the galaxy luminosity function (LF) and its dependence on local galaxy density, color, morphology, and clustocentric radius for the massive z=0.83 cluster MS 1054-0321. Our analyses are based on imaging performed with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST) in the F606W, F775W,…
Helium Line Formation and Abundance in a Solar Active Region
Andretta, V.; Teriaca, L.; Mauas, P. J. D. +3 more
An observing campaign (SOHO JOP 139), coordinated between ground-based and Solar and Heliospheric Observatory (SOHO) instruments, has been planned to obtain simultaneous spectroheliograms of the same active region in several spectral lines. The chromospheric lines Ca II K, Hα, and Na I D, as well as He I 10830, 5876, 584, and He II 304 Å lines hav…
A Small X-Ray Corona of the Narrow-Angle Tail Radio Galaxy NGC 1265 Soaring through the Perseus Cluster
Sun, M.; Jones, C.; Jerius, D.
A deep Chandra observation of NGC 1265 (3C 83.1B), the prototype for the narrow-angle tail (NAT) radio galaxy, reveals a small cool X-ray thermal corona (~0.6 keV) embedded in the hot ICM of the Perseus cluster (~6.7 keV). The corona is asymmetric with a sharp edge (~2.2", or 0.8 kpc from the nucleus) to the south and an extension to the north (at…
Magnetic Properties at Footpoints of Hot and Cool Loops
Tsuneta, Saku; Katsukawa, Yukio
Observations of the solar corona with Yohkoh, the Solar and Heliospheric Observatory, and the Transition Region and Coronal Explorer (TRACE) have revealed that individual coronal loops of active regions have their own temperatures from 1 to 5 MK. The hot (2-5 MK) Soft X-Ray Telescope (SXT) loops appear to require more heating energy than the cool …
High-Cadence Radio Observations of an EIT Wave
Thompson, B. J.; White, S. M.
Sensitive radio observations of the 1997 September 24 EIT wave show its velocity to be 830 km s-1. The wave first appears a short distance from the flare site, and its trajectory projects back to the flare site at the peak of the impulsive phase. The radio spectrum appears to be consistent with optically thin coronal emission rather tha…