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The Intrinsically X-Ray Weak Quasar PHL 1811. I. X-Ray Observations and Spectral Energy Distribution
Jenkins, Edward B.; Halpern, Jules P.; Leighly, Karen M. +3 more
This is the first of two papers reporting observations and analysis of the unusually bright (mb=14.4), luminous (MB=-25.5), nearby (z=0.192) narrow-line quasar PHL 1811, focusing on the X-ray properties and the spectral energy distribution. Two Chandra observations reveal a weak X-ray source with a steep spectrum. Variability…
Enceladus: Cosmic Graffiti Artist Caught in the Act
Verbiscer, Anne; Helfenstein, Paul; Showalter, Mark +1 more
As one of the most geologically active bodies in the solar system, Saturn's moon Enceladus not only coats itself with water ice particles, it accounts for the unusually high albedos of the other satellites orbiting within Saturn's vast, tenuous E ring. This effect is evident in Hubble Space Telescope observations obtained at true opposition on 13 …
4U 0115+63 from RXTE and INTEGRAL data: Pulse profile and cyclotron line energy
Sunyaev, R. A.; Tsygankov, S. S.; Lutovinov, A. A. +1 more
We analyze the observations of the transient X-ray pulsar 4U 0115+63 with the RXTE and INTEGRAL observatories in a wide X-ray (3-100 keV) energy band during its intense outbursts in 1999 and 2004. The energy of the fundamental harmonic of the cyclotron resonance absorption line near the maximum of the X-ray flux from the source (luminosity range 5…
The effect of stellar-mass black holes on the structural evolution of massive star clusters
Davies, M. B.; Mackey, A. D.; Wilkinson, M. I. +1 more
We present the results of realistic N-body modelling of massive star clusters in the Magellanic Clouds, aimed at investigating a dynamical origin for the radius-age trend observed in these systems. We find that stellar-mass black holes, formed in the supernova explosions of the most massive cluster stars, can constitute a dynamically important pop…
Photolytically Generated Aerosols in the Mesosphere and Thermosphere of Titan
Shemansky, Donald E.; Liang, Mao-Chang; Yung, Yuk L.
Analysis of the Cassini Ultraviolet Imaging Spectrograph (UVIS) stellar and solar occultations at Titan to date include 12 species: N2 (nitrogen), CH4 (methane), C2H2 (acetylene), C2H4 (ethylene), C2H6 (ethane), C4H2 (diacetylene), C6…
ACS imaging of star clusters in M 51. I. Identification and radius distribution
Bastian, N.; Larsen, S. S.; Gieles, M. +3 more
Context: Size measurements of young star clusters are valuable tools to put constraints on the formation and early dynamical evolution of star clusters.
Aims: We use HST/ACS observations of the spiral galaxy M 51 in F435W, F555W and F814W to select a large sample of star clusters with accurate effective radius measurements in an area covering …
High-latitude plasma convection from Cluster EDI measurements: method and IMF-dependence
Haaland, S. E.; Torbert, R. B.; Quinn, J. M. +6 more
We have used vector measurements of the electron drift velocity made by the Electron Drift Instrument (EDI) on Cluster between February 2001 and March 2006 to derive statistical maps of the high-latitude plasma convection. The EDI measurements, obtained at geocentric distances between ~4 and ~20 RE over both hemispheres, are mapped into…
Cluster observations of waves in the whistler frequency range associated with magnetic reconnection in the Earth's magnetotail
Dandouras, I.; Lucek, E.; RèMe, H. +7 more
On 21 August 2002 the Cluster spacecraft encountered a quasi-collisionless magnetic reconnection event when it crossed the plasma sheet. Prior to the southward turning of magnetic field in the tailward flow, the weak whistler waves were first observed. The burst of whistler waves appeared about 30 s earlier than the southward turning. During magne…
Morphology and dynamics of the upper cloud layer of Venus
Jaumann, R.; Keller, H. U.; Thomas, N. +7 more
Venus is completely covered by a thick cloud layer, of which the upper part is composed of sulphuric acid and some unknown aerosols. The cloud tops are in fast retrograde rotation (super-rotation), but the factors responsible for this super-rotation are unknown. Here we report observations of Venus with the Venus Monitoring Camera on board the Ven…
Hierarchical star formation in M33: fundamental properties of the star-forming regions
Bastian, N.; Gutermuth, R.; Gieles, M. +4 more
Star formation within galaxies appears on multiple scales, from spiral structure, to OB associations, to individual star clusters, and often substructure within these clusters. This multitude of scales calls for objective methods to find and classify star-forming regions, regardless of spatial size. To this end, we present an analysis of star-form…