Search Publications
Imaging of Titan from the Cassini spacecraft
Dones, Luke; Porco, Carolyn C.; McEwen, Alfred +33 more
Titan, the largest moon of Saturn, is the only satellite in the Solar System with a substantial atmosphere. The atmosphere is poorly understood and obscures the surface, leading to intense speculation about Titan's nature. Here we present observations of Titan from the imaging science experiment onboard the Cassini spacecraft that address some of …
Deflection of the Interstellar Neutral Hydrogen Flow Across the Heliospheric Interface
Bertaux, J. L.; Lallement, R.; Quémerais, E. +3 more
Using an absorption cell, we measured the Doppler shifts of the interstellar hydrogen resonance glow to show the direction of the neutral hydrogen flow as it enters the inner heliosphere. The neutral hydrogen flow is found to be deflected relative to the helium flow by about 4°. The most likely explanation of this deflection is a distortion of the…
The all-sky distribution of 511 keV electron-positron annihilation emission
Knödlseder, J.; Schanne, S.; Schönfelder, V. +11 more
We present a map of 511 keV electron-positron annihilation emission, based on data accumulated with the SPI spectrometer aboard ESA's INTEGRAL gamma-ray observatory, that covers approximately ~95% of the celestial sphere. Within the exposed sky area, 511 keV line emission is significantly detected towards the galactic bulge region and, at a very l…
Decay of Planetary Debris Disks
Bryden, G.; Stapelfeldt, K. R.; Rieke, G. H. +9 more
We report new Spitzer 24 µm photometry of 76 main-sequence A-type stars. We combine these results with previously reported Spitzer 24 µm data and 24 and 25 µm photometry from the Infrared Space Observatory and the Infrared Astronomy Satellite. The result is a sample of 266 stars with mass close to 2.5 Msolar, all detec…
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…