Search Publications
Lightning storms on Saturn observed by Cassini ISS and RPWS during 2004 2006
Porco, Carolyn C.; Dyudina, Ulyana A.; Ingersoll, Andrew P. +7 more
We report on Cassini Imaging Science Subsystem (ISS) data correlated with Radio and Plasma Wave Science (RPWS) observations, which indicate lightning on Saturn. A rare bright cloud erupt at ∼35° South planetocentric latitude when radio emissions (Saturn Electrostatic Discharges, or SEDs) occur. The cloud consisting of few consecutive eruptions typ…
An absorption origin for the soft excess in Seyfert 1 active galactic nuclei
Done, Chris; Gierliński, Marek; Middleton, Matthew
The soft excess seen in the X-ray spectra of many active galactic nuclei (AGN) can be well modelled by reflection from a partially ionized accretion disc. However, this often requires extreme parameters, both in terms of the underlying space-time and the reflection geometry, and requires that the disc is far from hydrostatic equilibrium. An altern…
X-rays from T Tauri: a test case for accreting T Tauri stars
Audard, M.; Güdel, M.; Briggs, K. R. +3 more
Context: The generation of X-rays in accreting T Tauri stars (TTS) is thought to be predominantly due to energy dissipation in magnetic fields, but alternative X-ray generation mechanisms have been proposed, such as heating in accretion shocks near the stellar surface, or in shocks forming in jets.
Aims: We test models and trends discussed in …
TRAMS: A new dynamic cloud model for Titan's methane clouds
Barth, Erika L.; Rafkin, Scot C. R.
Convective clouds on Titan may play an important role in climate dynamics, atmospheric chemistry, and the overall volatile cycle. To study the formation and evolution of these clouds, we have developed the Titan Regional Atmospheric Modeling System (TRAMS). TRAMS is a three-dimensional, time-dependent, coupled fully compressible dynamic and microp…
The Radio-Coronal Mass Ejection Event on 2001 April 15
Maia, Dalmiro Jorge Filipe; Gama, Ricardo; Mercier, Claude +3 more
On 2001 April 15, the Nançay radioheliograph observed fast-moving, expanding loops in images taken in the wavelength range between 164 and 432 MHz. We were able to follow the progression of the radio loops, starting from a few tenths to more than 1 Rsolar above the solar limb, with a time cadence of order seconds. The loops seen in radi…
Hubble Space Telescope Survey of Interstellar 12CO/13CO in the Solar Neighborhood
Gredel, R.; Lambert, D. L.; Federman, S. R. +2 more
We examine 20 diffuse and translucent Galactic sight lines and extract the column densities of the 12CO and 13CO isotopologues from their ultraviolet A-X absorption bands detected in archival Space Telescope Imaging Spectrograph data with λ/Δλ>=46,000. Five more targets with Goddard High-Resolution Spectrograph data are ad…
Hyperion's sponge-like appearance
Burns, J. A.; Denk, T.; Porco, C. +15 more
Hyperion is Saturn's largest known irregularly shaped satellite and the only moon observed to undergo chaotic rotation. Previous work has identified Hyperion's surface as distinct from other small icy objects but left the causes unsettled. Here we report high-resolution images that reveal a unique sponge-like appearance at scales of a few kilometr…
Gravitational Shear, Flexion, and Strong Lensing in Abell 1689
Massey, Richard; Goldberg, David M.; Leonard, Adrienne +1 more
We present a gravitational lensing analysis of the galaxy cluster Abell 1689, incorporating measurements of the weak shear, flexion, and strong lensing induced in background galaxies. This is the first time that a shapelet technique has been used to reconstruct the distribution of mass in this cluster and the first time that a flexion signal has b…
The composition of Saturn's E ring
Kempf, S.; Postberg, F.; Srama, R. +7 more
We present the first in situ direct measurement of the composition of particles in Saturn's rings. The Cassini cosmic dust analyser (CDA) measured the mass spectra of nearly 300 impacting dust particles during the 2004 October E ring crossing. An initial interpretation of the data shows that the particles are predominantly water ice, with minor co…
Testing the accuracy of synthetic stellar libraries
Coelho, Paula; Martins, Lucimara P.
One of the main ingredients of stellar population synthesis models is a library of stellar spectra. Both empirical and theoretical libraries are used for this purpose, and the question about which one is preferable is still debated in the literature. Empirical and theoretical libraries are being improved significantly over the years, and many libr…