Search Publications
Physical Characteristics and Non-Keplerian Orbital Motion of "Propeller" Moons Embedded in Saturn's Rings
Porco, Carolyn C.; Hedman, Matthew M.; Burns, Joseph A. +8 more
We report the discovery of several large "propeller" moons in the outer part of Saturn's A ring, objects large enough to be followed over the 5 year duration of the Cassini mission. These are the first objects ever discovered that can be tracked as individual moons, but do not orbit in empty space. We infer sizes up to 1-2 km for the unseen moonle…
The ultraviolet reflectance of Enceladus: Implications for surface composition
Hendrix, Amanda R.; Hansen, Candice J.; Holsclaw, Greg M.
The reflectance of Saturn's moon Enceladus has been measured at far ultraviolet (FUV) wavelengths (115-190 nm) by Cassini's Ultraviolet Imaging Spectrograph (UVIS). At visible and near infrared (VNIR) wavelengths Enceladus' reflectance spectrum is very bright, consistent with a surface composed primarily of H 2O ice. At FUV wavelengths,…
Dayside induced magnetic field in the ionosphere of Mars
Gurnett, D. A.; Morgan, D. D.; Modolo, R. +5 more
The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) onboard the Mars Express spacecraft has occasionally displayed surprising features. One such feature is the occurrence of a series of broadband, low-frequency echoes at equally spaced delay times after the sounder transmitter pulse. The interval between the echoes has been sh…
X-ray, FUV, and UV Observations of α Centauri B: Determination of Long-term Magnetic Activity Cycle and Rotation Period
Guinan, E. F.; DeWarf, L. E.; Datin, K. M.
Over the last couple of decades we have been carrying out a study of stellar magnetic activity, dynamos, atmospheric physics, and spectral irradiances from a sample of solar-type G0-5 V stars with different ages. One of the major goals of this program is to study the evolution of the Sun's X-ray through NUV spectral irradiances with age. Of partic…
Variability and the X-ray/UV ratio of active galactic nuclei
Trevese, D.; Vagnetti, F.; Antonucci, M. +1 more
Context. The observed relation between the X-ray radiation from active galactic nuclei, originating in the corona, and the optical/UV radiation from the disk is usually described by the anticorrelation between the UV to X-ray slope α_ox and the UV luminosity. Many factors can affect this relation, including: i) enhanced X-ray emission associated w…
The Origin and Evolution of the Halo PN BoBn 1: From a Viewpoint of Chemical Abundances Based on Multiwavelength Spectra
Izumiura, Hideyuki; Otsuka, Masaaki; Hyung, Siek +1 more
We have performed a comprehensive chemical abundance analysis of the extremely metal-poor ([Ar/H] < -2) halo planetary nebula (PN) BoBn 1 based on International Ultraviolet Explorer archive data, Subaru/High-Dispersion Spectrograph spectra, VLT/UVES archive data, and Spitzer/IRS spectra. We have detected over 600 lines in total and calculated i…
Modeling the Surface X-ray Emission and Viewing Geometry of PSR J0821-4300 in Puppis A
Gotthelf, E. V.; Halpern, J. P.; Perna, R.
We present a model for the unusual X-ray pulse profiles of PSR J0821-4300, the compact central object in supernova remnant Puppis A. We show that a pair of thermal, antipodal hot spots on the neutron star (NS) surface is able to fully account for the pulsar's double blackbody spectrum and energy-dependent pulse profile, including the observed 180°…
Surface structure of the CoRoT CP2 target star HD 50773
Donati, J. -F.; Petit, P.; Baudin, F. +15 more
Aims: We compare surface maps of the chemically peculiar star HD 50773 produced with a Bayesian technique and based on high quality CoRoT photometry with those derived from rotation phase resolved spectropolarimetry. The goal is to investigate the correlation of surface brightness with surface chemical abundance distribution and the stellar m…
The HST/ACS Coma Cluster Survey. II. Data Description and Source Catalogs
Ferguson, Henry C.; Mobasher, Bahram; Miller, Bryan W. +46 more
The Coma cluster, Abell 1656, was the target of an HST-ACS Treasury program designed for deep imaging in the F475W and F814W passbands. Although our survey was interrupted by the ACS instrument failure in early 2007, the partially completed survey still covers ~50% of the core high-density region in Coma. Observations were performed for 25 fields …
The Herschel view of star formation in the Rosette molecular cloud under the influence of NGC 2244
Olofsson, G.; Abergel, A.; Hill, T. +43 more
Context. The Rosette molecular cloud is promoted as the archetype of a triggered star-formation site. This is mainly due to its morphology, because the central OB cluster NGC 2244 has blown a circular-shaped cavity into the cloud and the expanding H II-region now interacts with the cloud.
Aims: Studying the spatial distribution of the differe…