Search Publications
Cassini observations of ionospheric photoelectrons at large distances from Titan: Implications for Titan's exospheric environment and magnetic tail
Lewis, G. R.; Coates, A. J.; Jones, G. H. +6 more
Discrete peaks near 24.1 eV are seen in electron spectra measured in Titan's ionosphere by the ELS (Electron Spectrometer), part of the Cassini Plasma Spectrometer (CAPS), and are interpreted as photoelectrons. These photoelectrons are generated as a result of ionization of N2 by the strong solar He II (30.4 nm) line. They are generally…
The influence of spectral solar irradiance data on stratospheric heating rates during the 11 year solar cycle
Weber, M.; Solanki, S. K.; Krivova, N. A. +7 more
Heating rate calculations with the FUBRad shortwave (SW) radiation parameterization have been performed to examine the effect of prescribed spectral solar fluxes from the NRLSSI, MPS and IUP data sets on SW heating rates over the 11 year solar cycle 22. The corresponding temperature response is derived from perpetual January General Circulation Mo…
Model Selection for Spectropolarimetric Inversions
Orozco Suárez, D.; Asensio Ramos, A.; Martínez González, M. J. +3 more
Inferring magnetic and thermodynamic information from spectropolarimetric observations relies on the assumption of a parameterized model atmosphere whose parameters are tuned by comparison with observations. Often, the choice of the underlying atmospheric model is based on subjective reasons. In other cases, complex models are chosen based on obje…
The Kinematics of HH 34 from HST Images with a Nine-year Time Baseline
Stapelfeldt, K. R.; Raga, A. C.; Lora, V. +3 more
We study archival HST [S II] 6716+30 and Hα images of the HH 34 outflow, taken in 1998.71 and in 2007.83. The ~9 yr time baseline and the high angular resolution of these observations allow us to carry out a detailed proper-motion study. We determine the proper motions of the substructure of the HH 34S bow shock (from the [S II] and Hα frames) and…
LBQS 0103-2753: A Binary Quasar in a Major Merger
Junkkarinen, V.; Shields, G. A.; Chapman, S. C. +3 more
We present Hubble Space Telescope (HST) and United Kingdom Infrared Telescope spectra and images of the 2 kpc (0farcs3) binary quasar LBQS 0103-2753 (z = 0.858). The HST images (V and I bands) show tidal features demonstrating that this system is a major galaxy merger in progress. A two-color composite image brings out knots of star formation alon…
Saturn's F ring as seen by Cassini UVIS: Kinematics and statistics
Colwell, Joshua E.; Esposito, Larry W.; Sremčević, Miodrag +1 more
We present a new orbital model of Saturn's F ring core based on 93 occultations by the Cassini Ultraviolet Imaging Spectrograph (UVIS) and the Voyager radio and stellar occultations. We demonstrate that the core, despite its intrinsic variability, is well-described as an inclined, freely precessing ellipse. We find that post-fit residuals with a r…
Data and two-dimensional scaling relations for galaxies in Abell 1689: a hint of size evolution at z∼ 0.2
Davies, Roger L.; Dalla Bontà, E.; Houghton, R. C. W. +1 more
We present imaging and spectroscopy of Abell 1689 (z= 0.183) from the Gemini multi-object spectrograph (GMOS) on the Gemini North telescope and the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). We measure integrated photometry from the GMOS g' and r' images (for 531 galaxies) and surface photometry from the HSTF625W image …
The cosmic history of hot gas cooling and radio active galactic nucleus activity in massive early-type galaxies
Lehmer, B. D.; Alexander, D. M.; Brandt, W. N. +5 more
We study the X-ray properties of 393 optically selected early-type galaxies (ETGs) over the redshift range of z≈ 0.0-1.2 in the Chandra Deep Fields (CDFs). To measure the average X-ray properties of the ETG population, we use X-ray stacking analyses with a subset of 158 passive ETGs (148 of which were individually undetected in X-ray). This ETG su…
Illumination conditions at the Asteroid 4 Vesta: Implications for the presence of water ice
Stubbs, Timothy J.; Wang, Yongli
The mean illumination conditions and surface temperatures over one orbital period are calculated for the Asteroid 4 Vesta using a coarse digital elevation model produced from Hubble Space Telescope images. Even with the anticipated effects of finer-scale topography taken into account, it is unlikely that any significant permanently shadowed region…
The pulse profile and spin evolution of the accreting pulsar in Terzan 5, IGR J17480-2446, during its 2010 outburst
Stella, L.; Tramacere, A.; Ferrigno, C. +9 more
We analyse the spectral and pulse properties of the 11 Hz transient accreting pulsar, IGR J17480-2446, in the globular cluster Terzan 5, considering all the available Rossi X-Ray Timing Explorer, Swift and INTEGRAL observations performed during the outburst shown between 2010 October and November.
By measuring the pulse phase evolution we con…