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Strong-Lensing Analysis of A1689 from Deep Advanced Camera Images
Herranz, D.; Zheng, W.; Broadhurst, Tom +39 more
We analyze deep multicolor Advanced Camera images of the largest known gravitational lens, A1689. Radial and tangential arcs delineate the critical curves in unprecedented detail, and many small counterimages are found near the center of mass. We construct a flexible light deflection field to predict the appearance and positions of counterimages. …
Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. I. A Reverberation-based Measurement of the Black Hole Mass
Kaspi, Shai; Laor, Ari; Moran, Edward C. +8 more
A reverberation-mapping program on NGC 4395, the least luminous known Seyfert 1 galaxy, undertaken with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope yields a measurement of the mass of the central black hole MBH=(3.6+/-1.1)×105 Msolar. The observations consist of two visits of five orbits …
Cosmological parameters from supernova observations: A critical comparison of three data sets
Choudhury, T. R.; Padmanabhan, T.
We extend our previous analysis of cosmological supernova type Ia data \cite{pc03} to include three recent compilation of data sets. Our analysis ignores the possible correlations and systematic effects present in the data and concentrates mostly on some key theoretical issues. Among the three data sets, the first set consists of 194 points obtain…
A simple test for periodic signals in red noise
Vaughan, S.
We demonstrate a simple method for testing the significance of peaks in the periodogram of red noise data. The procedure was designed to test for spurious periodicities in X-ray light curves of active galaxies, but can be used quite generally to test for periodic components against a background noise spectrum assumed to have a power law shape. The…
Direct Observations of the Magnetic Reconnection Site of an Eruption on 2003 November 18
Raymond, J. C.; Ko, Y. -K.; Lin, J. +5 more
We report direct observations of the magnetic reconnection site during an eruptive process that occurred on 2003 November 18. The event started with a rapid expansion of a few magnetic arcades located over the east limb of the Sun and developed an energetic partial-halo coronal mass ejection (CME), a long current sheet, and a group of bright flare…
Radial evolution of the electron distribution functions in the fast solar wind between 0.3 and 1.5 AU
McComas, D. J.; Maksimovic, M.; Issautier, K. +8 more
Observed electron distribution functions of the solar wind permanently exhibit three different components: a thermal core and a suprathermal halo, which are always present at all pitch angles, and a sharply magnetic field aligned "strahl" which is usually anti-sunward moving. Whereas Coulomb collisions can explain the relative isotropy of the core…
Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars
Jaumann, R.; Head, J. W.; Neukum, G. +11 more
Images from the Mars Express HRSC (High-Resolution Stereo Camera) of debris aprons at the base of massifs in eastern Hellas reveal numerous concentrically ridged lobate and pitted features and related evidence of extremely ice-rich glacier-like viscous flow and sublimation. Together with new evidence for recent ice-rich rock glaciers at the base o…
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…
Radar Soundings of the Subsurface of Mars
Gurnett, Donald A.; Johnson, William T. K.; Stofan, Ellen R. +31 more
The martian subsurface has been probed to kilometer depths by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument aboard the Mars Express orbiter. Signals penetrate the polar layered deposits, probably imaging the base of the deposits. Data from the northern lowlands of Chryse Planitia have revealed a shallowly buried quasi-…