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Doppler boosting, superluminal motion, and the kinematics of AGN jets
Kadler, M.; Ros, E.; Zensus, J. A. +8 more
We discuss results from a decade long program to study the fine-scale structure and the kinematics of relativistic AGN jets with the aim of better understanding the acceleration and collimation of the relativistic plasma forming AGN jets. From the observed distribution of brightness temperature, apparent velocity, flux density, time variability, a…
The Posteruptive Evolution of a Coronal Dimming
McIntosh, Scott W.; Davey, Alisdair R.; Leamon, Robert J. +1 more
We discuss the posteruptive evolution of a ``coronal dimming'' based on observations of the EUV corona from the Solar and Heliospheric Observatory and the Transition Region and Coronal Explorer (TRACE). This discussion highlights the roles played by magnetoconvection-driven magnetic reconnection and the global magnetic environment of the plasma in…
Seismic Study of the Chemical Composition of the Solar Convection Zone
Basu, Sarbani; Antia, H. M.; Lin, Chia-Hsien
Recent downward revision of solar heavy-element abundances using a three-dimensional atmospheric model has introduced serious discrepancies between standard solar models and helioseismic inferences about solar structure. In this paper we investigate the possibility of determining the heavy-element abundances using helioseismic inversion techniques…
Contamination by Surface Effects of Time-Distance Helioseismic Inversions for Sound Speed beneath Sunspots
Rajaguru, S. P.; Couvidat, S.
Using Doppler velocity data from the SOI/MDI instrument on board the SOHO spacecraft, we do time-distance helioseismic inversions for sound-speed perturbations beneath 16 sunspots observed in high-resolution mode. We clearly detect ringlike regions of enhanced sound speed beneath most sunspot penumbrae, extending from near the surface to depths of…
HESS J1616-508: likely to be powered by PSR J1617-5055
de Rosa, A.; Bird, A. J.; Ubertini, P. +3 more
HESS J1616-508 is one of the brightest emitters in the TeV sky. Recent observations with the IBIS/ISGRI telescope onboard the INTEGRAL spacecraft have revealed that a young, nearby and energetic pulsar, PSR J1617-5055, is a powerful emitter of soft γ-rays in the 20-100 keV domain. In this paper, we present an analysis of all available data from th…
Direct Measurement of the Radius and Density of the Transiting Exoplanet HD 189733b with the CHARA Array
Swain, Mark; van Belle, Gerard T.; McAlister, Harold A. +5 more
We have measured the angular diameter of the transiting extrasolar planet host star HD 189733 using the CHARA optical/IR interferometric array. Combining our new angular diameter of 0.377+/-0.024 mas with the Hipparcos parallax leads to a linear radius for the host star of 0.779+/-0.052 Rsolar and a radius for the planet of 1.19+/-0.08 …
Validation of Helioseismology through Forward Modeling: Realization Noise Subtraction and Kernels
Hanasoge, S. M.; Duvall, T. L., Jr.; Couvidat, S.
Through a series of numerical simulations of the near-surface acoustic wavefield of the Sun, we show the utility of the forward approach in local helioseismology. We demonstrate and apply a method to subtract a large fraction of the realization noise from the simulated data. The ability to attain high signal-to-noise ratios from brief forward calc…
An XMM-Newton view of the young open cluster NGC 6231 - III. Optically faint X-ray sources
Gosset, E.; Rauw, G.; Vreux, J. -M. +2 more
We discuss the properties of the X-ray sources with faint optical counterparts in the very young open cluster NGC 6231. From their positions in the Hertzsprung-Russell diagram, we find that the bulk of these objects probably consists of low-mass pre-main-sequence (PMS) stars with masses in the range 0.3-3.0 Msolar. The age distribution …
High-latitude plasma convection from Cluster EDI: variances and solar wind correlations
Haaland, S. E.; Torbert, R. B.; Quinn, J. M. +4 more
Based on drift velocity measurements of the EDI instruments on Cluster during the years 2001-2006, we have constructed a database of high-latitude ionospheric convection velocities and associated solar wind and magnetospheric activity parameters. In an earlier paper (Haaland et al., 2007), we have described the method, consisting of an improved te…
Halo Coronal Mass Ejections and Configuration of the Ambient Magnetic Fields
Liu, Y.
In this study, we seek a correlation between the speed of active region-related halo coronal mass ejections (CMEs) and the configuration of the ambient magnetic fields. Having studied 99 halo CMEs in the period from 2000 to 2004, we find that CMEs under the heliospheric current sheet are significantly slower than CMEs situated under unidirectional…