Search Publications
A periodicity of ~1hour in X-ray emission from the active galaxy RE J1034+396
Done, Chris; Ward, Martin; Gierliński, Marek +1 more
Active galactic nuclei and quasars are thought to be scaled-up versions of Galactic black hole binaries, powered by accretion onto supermassive black holes with masses of 106-109, as opposed to the ~10 in binaries (here is the solar mass). One example of the similarities between these two types of systems is the characteristi…
A High-Resolution Survey of Low-Redshift QSO Absorption Lines: Statistics and Physical Conditions of O VI Absorbers
Richter, Philipp; Bowen, David V.; Tripp, Todd M. +4 more
Using high-resolution ultraviolet spectra of 16 low-z QSOs obtained with the E140M echelle mode of the Space Telescope Imaging Spectrograph, we study the physical conditions and statistics of O VI absorption in the intergalactic medium (IGM) at z < 0.5. We identify 51 intervening (zabsll zQSO) O VI systems comprising 77 in…
The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851
Anderson, J.; Milone, A. P.; Sarajedini, A. +13 more
Photometry with the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) reveals that the subgiant branch (SGB) of the globular cluster NGC 1851 splits into two well-defined branches. If the split is due only to an age effect, the two SGBs would imply two star formation episodes separated by ~1 Gyr. We discuss other anomalies in NGC 1851 t…
Revealing the Properties of Dark Matter in the Merging Cluster MACS J0025.4-1222
Treu, Tommaso; Bradač, Maruša; Allen, Steven W. +5 more
We constrain the physical nature of dark matter using the newly identified massive merging galaxy cluster MACS J0025.4-1222. As was previously shown by the example of the Bullet Cluster (1E 0657-56), such systems are ideal laboratories for detecting isolated dark matter and distinguishing between cold dark matter (CDM) and other scenarios (e.g., s…
Nonlinear Force-free Field Modeling of a Solar Active Region around the Time of a Major Flare and Coronal Mass Ejection
Aulanier, G.; Schrijver, C. J.; Amari, T. +14 more
Solar flares and coronal mass ejections are associated with rapid changes in field connectivity and are powered by the partial dissipation of electrical currents in the solar atmosphere. A critical unanswered question is whether the currents involved are induced by the motion of preexisting atmospheric magnetic flux subject to surface plasma flows…
Coupling photochemistry with haze formation in Titan's atmosphere, Part II: Results and validation with Cassini/Huygens data
Coustenis, A.; Lavvas, P. P.; Vardavas, I. M.
The new one-dimensional radiative-convective/photochemical/microphysical model described in Part I is applied to the study of Titan's atmospheric processes that lead to haze formation. Our model generates the haze structure from the gaseous species photochemistry. Model results are presented for the species vertical concentration profiles, haze fo…
Flare Observations
Benz, Arnold O.
Solar flares are observed at all wavelengths from decameter radio waves to gamma-rays at 100 MeV. This review focuses on recent observations in EUV, soft and hard X-rays, white light, and radio waves. Space missions such as RHESSI, Yohkoh, TRACE, and SOHO have enlarged widely the observational base. They have revealed a number of surprises: Corona…
The first XMM-Newton slew survey catalogue: XMMSL1
Altieri, B.; Read, A. M.; Esquej, P. +3 more
Aims:We report on the production of a large area, shallow, sky survey, from XMM-Newton slews. The great collecting area of the mirrors coupled with the high quantum efficiency of the EPIC detectors have made XMM-Newton the most sensitive X-ray observatory flown to date. We use data taken with the EPIC-pn camera during slewing manoeuvres to perform…
Image Stabilization System for Hinode (Solar-B) Solar Optical Telescope
Ichimoto, K.; Kobayashi, K.; Tsuneta, S. +16 more
The Hinode Solar Optical Telescope (SOT) is the first space-borne visible-light telescope that enables us to observe magnetic-field dynamics in the solar lower atmosphere with 0.2 - 0.3 arcsec spatial resolution under extremely stable (seeing-free) conditions. To achieve precise measurements of the polarization with diffraction-limited images, sta…
An Infrared Survey of Brightest Cluster Galaxies. II. Why are Some Brightest Cluster Galaxies Forming Stars?
Baum, Stefi A.; O'Dea, Christopher P.; Sarazin, Craig L. +12 more
Quillen et al. presented an imaging survey with the Spitzer Space Telescope of 62 brightest cluster galaxies with optical line emission located in the cores of X-ray-luminous clusters. They found that at least half of these sources have signs of excess IR emission. Here we discuss the nature of the IR emission and its implications for cool core cl…