Search Publications
An X-Ray Study of Magnetic Field Strengths and Particle Content in the Lobes of FR II Radio Sources
Hardcastle, M. J.; Croston, J. H.; Birkinshaw, M. +3 more
We present a Chandra and XMM-Newton study of X-ray emission from the lobes of 33 classical double radio galaxies and quasars. We report new detections of lobe-related X-ray emission in 11 sources. Together with previous detections, we find that X-ray emission is detected from at least one radio lobe in ~75% of the sample. For all of the lobe detec…
Measurement of Spin-Orbit Alignment in an Extrasolar Planetary System
Butler, R. Paul; Vogt, Steven S.; Marcy, Geoffrey W. +10 more
We determine the stellar, planetary, and orbital properties of the transiting planetary system HD 209458 through a joint analysis of high-precision radial velocities, photometry, and timing of the secondary eclipse. Of primary interest is the strong detection of the Rossiter-McLaughlin effect, the alteration of photospheric line profiles that occu…
Reflections of Active Galactic Nucleus Outbursts in the Gaseous Atmosphere of M87
Churazov, E.; Vikhlinin, A.; Forman, W. +7 more
We combined deep Chandra, ROSAT HRI, and XMM-Newton observations of M87 to study the impact of active galactic nucleus (AGN) outbursts on its gaseous atmosphere. Many X-ray features appear to be a direct result of repetitive AGN outbursts. In particular, the X-ray cavities around the jet and counterjet are likely due to the expansion of radio plas…
Helioseismological Implications of Recent Solar Abundance Determinations
Pinsonneault, Marc; Basu, Sarbani; Bahcall, John N. +1 more
We show that standard solar models are in good agreement with the helioseismologically determined sound speed and density as a function of solar radius, the depth of the convective zone, and the surface helium abundance, as long as those models do not incorporate the most recent heavy-element abundance determinations. However, sophisticated new an…
Rapid Compton-thick/Compton-thin Transitions in the Seyfert 2 Galaxy NGC 1365
Zezas, A.; Elvis, M.; Baldi, A. +2 more
We present multiple Chandra and XMM-Newton observations of the type 1.8 Seyfert galaxy NGC 1365, which shows the most dramatic X-ray spectral changes observed so far in an active galactic nucleus: the source switched from reflection-dominated to transmission-dominated and back in just 6 weeks. During this time the soft thermal component, arising f…
An Ab Initio Approach to the Solar Coronal Heating Problem
Nordlund, Åke; Gudiksen, Boris Vilhelm
We present an ab initio approach to the solar coronal heating problem by modeling a small part of the solar corona in a computational box using a three-dimensional MHD code including realistic physics. The observed solar granular velocity pattern and its amplitude and vorticity power spectra, as reproduced by a weighted Voronoi tessellation method…
Making the Corona and the Fast Solar Wind: A Self-consistent Simulation for the Low-Frequency Alfvén Waves from the Photosphere to 0.3 AU
Inutsuka, Shu-ichiro; Suzuki, Takeru K.
By performing a one-dimensional magnetohydrodynamic simulation with radiative cooling and thermal conduction, we show that the coronal heating and the fast solar wind acceleration in the coronal holes are natural consequences of the footpoint fluctuations of the magnetic fields at the photosphere. We initially set up a static open flux tube with a…
The Relationship of Hard X-Ray and Optical Line Emission in Low-Redshift Active Galactic Nuclei
Ptak, A.; Heckman, T. M.; Hornschemeier, A. +1 more
In this paper we assess the relationship of the population of active galactic nuclei (AGNs) selected by hard X-rays to the traditional population of AGNs with strong optical emission lines. First, we study the emission-line properties of a new hard-X-ray-selected sample of 47 local AGNs (classified optically as Type 1 and 2 AGNs). We find that the…
The ACS Virgo Cluster Survey. VII. Resolving the Connection between Globular Clusters and Ultracompact Dwarf Galaxies
Djorgovski, S. G.; Jordán, Andrés; Tonry, John L. +10 more
We investigate the connection between globular clusters and ultracompact dwarf galaxies (UCDs) by examining the properties of 10 compact, high-luminosity (-11.8 MV -10.8) objects associated with M87 (NGC 4486, VCC 1316), the cD galaxy in the Virgo Cluster. These objects, most of which were previously classified as M87 globular clusters, were selec…
The ACS Virgo Cluster Survey. X. Half-Light Radii of Globular Clusters in Early-Type Galaxies: Environmental Dependencies and a Standard Ruler for Distance Estimation
Sarazin, Craig L.; Jordán, Andrés; Tonry, John L. +10 more
We have measured half-light radii, rh, for thousands of globular clusters (GCs) belonging to the 100 early-type galaxies observed in the ACS Virgo Cluster Survey and the elliptical galaxy NGC 4697. An analysis of the dependencies of the measured half-light radii on both the properties of the GCs themselves and their host galaxies reveal…