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High-frequency oscillations in a solar active region coronal loop
Mathioudakis, M.; Keenan, F. P.; Phillips, K. J. H. +6 more
The Solar Eclipse Corona Imaging System (SECIS) was used to record high-cadence observations of the solar corona during the total solar eclipse of 1999 August 11. During the 2min 23.5s of totality, 6364 images were recorded simultaneously in each of the two channels: a white light channel, and the Fexiv (5303Å) `green line' channel (T~2MK). Here w…
The Ionization and Metallicity of the Intervening O VI Absorber at z=0.1212 in the Spectrum of H1821+643
Tripp, Todd M.; Stocke, John T.; Tumlinson, Jason +2 more
We use high-resolution UV spectra of the radio-quiet quasar (QSO) H1821+643 (zem=0.297), obtained with the Space Telescope Imaging Spectrograph (STIS) and the Far Ultraviolet Spectroscopic Explorer (FUSE), to study the ionization and metallicity of an intervening O VI absorption line system at zabs=0.1212. This absorber has t…
A Pair of Compact Red Galaxies at Redshift 2.38, Immersed in a 100 Kiloparsec Scale Lyα Nebula
Teplitz, Harry I.; Kimble, Randy A.; Sutherland, Ralph S. +12 more
We present Hubble Space Telescope and ground-based observations of a pair of galaxies at a redshift of 2.38, which are collectively known as 2142-4420 B1. Both galaxies are luminous extremely red objects (EROs) and are separated by 0.8". They are embedded within a 100 kpc scale diffuse Lyα nebula (or blob) of luminosity ~1044 ergs s
New light on the X-ray spectrum of the Crab Nebula
Warwick, R. S.; Aschenbach, B.; Becker, W. +5 more
XMM-Newton observations of the Crab provide new information on its integrated X-ray spectrum and the variation of the spectral form across the nebula. The Crab pulsar and its surrounding torus exhibit the hardest spectra with power-law indices of Gamma = 1.6 and 1.8. The jet and outer reaches of the nebula are significantly softer with Gamma = 2.1…
Chandra Reveals the X-Ray Glint in the Cat's Eye
Guerrero, Martín A.; Chu, You-Hua; Gruendl, Robert A. +2 more
We have obtained Chandra ACIS-S observations of NGC 6543, the Cat's Eye Nebula. The X-ray emission from NGC 6543 is clearly resolved into a point source at the central star and diffuse emission confined within the central elliptical shell and two extensions along the major axis. Spectral analysis of the diffuse component shows that the abundances …
A Multiwavelength Study of Stephan's Quintet
Trinchieri, Ginevra; Xu, Cong; Sulentic, Jack W. +4 more
Stephan's Quintet (SQ) is a compact group that we find in an atypical moment when a high-velocity intruder is passing through it. The intrusion is particularly interesting because a previous intruder had stripped most of the gas from the group members. This debris field was shocked in the ongoing collision with the new intruder. This evolutionary …
Fractal Structure in Galactic Star Fields
Elmegreen, Bruce G.; Elmegreen, Debra Meloy
The fractal structure of star formation on large scales in disk galaxies is studied using the size distribution function of stellar aggregates in kiloparsec-scale star fields. Archival Hubble Space Telescope images of 10 galaxies are Gaussian-smoothed to define the aggregates, and a count of these aggregates versus smoothing scale gives the fracta…
Comprehensive Photometry of the Rings and 16 Satellites of Uranus with the Hubble Space Telescope
Karkoschka, Erich
Photometric properties of 4 rings and 16 satellites of Uranus are presented, based on 41 Hubble Space Telescope images taken in 1997. Up to 25 filters per object covered the wavelength range 0.27-2 µm. The whole range of phase angles observable from Earth (0.03-3°) was probed. Reflectivities were calibrated on an absolute scale to typically …
Blue Stragglers, Young White Dwarfs, and UV-Excess Stars in the Core of 47 Tucanae
Ferraro, Francesco R.; Paltrinieri, Barbara; Possenti, Andrea +2 more
We used a set of archived Hubble Space Telescope/WFPC2 images to probe the stellar population in the core of the nearby galactic globular cluster (GGC) 47 Tuc. From the ultraviolet (UV) color magnitude diagrams (CMDs) obtained for ~4000 stars detected within the Planetary Camera (PC) field of view we have pinpointed a number of interesting objects…
A Chandra Study of the Circinus Galaxy Point-Source Population
Bauer, F. E.; Brandt, W. N.; Netzer, H. +4 more
We have used the Chandra X-Ray Observatory to resolve spatially and spectrally the X-ray emission from the Circinus galaxy. We report here on the nature of the X-ray emission from the off-nuclear point sources associated with the disk of Circinus, which make up ~34% of the total 0.5-10 keV emission. We find that many of the serendipitous X-ray sou…