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The Local Lyα Forest. III. Relationship between Lyα Absorbers and Galaxies, Voids, and Superclusters
Shull, J. Michael; Stocke, John T.; Penton, Steven V.
In this paper we use large-angle, nearby galaxy redshift surveys to investigate the relationship between the 81 low-redshift Lyα absorbers in our Hubble Space Telescope GHRS survey and galaxies, superclusters, and voids. In a subsample of 46 Lyα absorbers located in regions where the 2000 February 8 CfA catalog is complete down to at least L* gala…
The Stellar Velocity Dispersion of the Lens Galaxy in MG 2016+112 at z=1.004
Treu, Tommaso; Koopmans, Léon V. E.
We present a direct measurement of the stellar velocity dispersion of the early-type lens galaxy D in the system MG 2016+112 (z=1.004), determined from a spectrum obtained with the Echelle Spectrograph and Imager on the W. M. Keck II Telescope, as part of the Lenses Structure and Dynamics Survey. We find a velocity dispersion of σap=304…
Chandra Observations of the Lensing Cluster EMSS 1358+6245: Implications for Self-interacting Dark Matter
Garmire, G. P.; Bautz, M. W.; Arabadjis, J. S.
We present Chandra observations of EMSS 1358+6245, a relaxed cooling flow cluster of galaxies at z=0.328. We employ a new deprojection technique to construct temperature, gas, and dark matter profiles. We confirm the presence of cool gas in the cluster core, and our deprojected temperature profile for the hot component is isothermal over 30kpc<…
Energy Distribution of Microevents in the Quiet Solar Corona
Krucker, Säm; Benz, Arnold O.
Recent imaging observations of EUV line emissions have shown evidence for frequent flarelike events in a majority of the pixels in quiet regions of the solar corona. The changes in coronal emission measure indicate impulsive heating of new material to coronal temperatures. These heating or evaporation events are candidate signatures of ``nanoflare…
An XMM-Newton Study of the 401 Hz Accreting Pulsar SAX J1808.4-3658 in Quiescence
Campana, S.; Mereghetti, S.; Stella, L. +6 more
SAX J1808.4-3658 is a unique source, being the first low-mass X-ray binary showing coherent pulsations at a spin period comparable to that of millisecond radio pulsars. Here we present an XMM-Newton observation of SAX J1808.4-3658 in quiescence, the first that assessed its quiescent luminosity and spectrum with a good signal-to-noise ratio. XMM-Ne…
Chandra Observations of the X-Ray Jet in Centaurus A
Hardcastle, M. J.; Worrall, D. M.; Forman, W. R. +3 more
We present high angular resolution X-ray images and spectra from two Chandra AXAF CCD Imaging Spectrometer (ACIS-I) observations of the X-ray jet in the nearby radio galaxy Cen A. We find that the X-ray emission from the jet is composed of a low surface brightness diffuse component extending continuously from within at least 60 pc of the active nu…
The Hydromagnetic Origin of the Two Dynamical Types of Solar Coronal Mass Ejections
Zhang, M.; Low, B. C.
We propose a qualitative theory relating flux rope coronal mass ejections (CMEs) to initial states, represented by inverse or normal quiescent prominences corresponding to whether the flux rope magnetic field circulates in the same or opposite sense relative to the surrounding coronal magnetic field. Our theory explains the observed dual character…
Chandra Discovery of a 300 Kiloparsec X-Ray Jet in the Gigahertz-peaked Spectrum Quasar PKS 1127-145
Elvis, Martin; Bechtold, Jill; Harris, D. E. +3 more
We have discovered an X-ray jet with Chandra imaging of the z=1.187 radio-loud quasar PKS 1127-145. In this paper we present the Chandra X-ray data, follow-up Very Large Array observations, and optical imaging using the Hubble Space Telescope Wide Field Planetary Camera 2. The X-ray jet contains 273+/-5 net counts in 27 ks and extends ~30" from th…
A Second Planet Orbiting 47 Ursae Majoris
Butler, R. Paul; Vogt, Steven S.; Fischer, Debra A. +2 more
Precise Doppler velocity measurements during 13 yr at Lick Observatory reveal the presence of two planets orbiting the star 47 UMa. The previously detected inner planet is confirmed by the newer velocities that yield a revised orbital period Pb=1089.0+/-2.9 days, Msini=2.54 MJ, and eccentricity eb=0.061+/-0.014. Th…
The Parallax and Proper Motion of RX J1856.5-3754 Revisited
van Kerkwijk, M. H.; Anderson, J.; Kaplan, D. L.
RX J1856.5-3754, a bright soft X-ray source believed to be the nearest thermally emitting neutron star, has commanded and continues to command intense interest from X-ray missions. One of the main goals is to determine the radius of this neutron star. An integral part of the determination is an accurate parallax. F. M. Walter analyzed Hubble Space…