Search Publications
The structure and time variability of the ring atmosphere and ionosphere
Johnson, R. E.; Ip, W. -H.; Elrod, M. K. +2 more
The saturnian system is subject to constant bombardment by interplanetary meteoroids and irradiation by solar UV photons. Both effects release neutral molecules from the icy ring particles either in the form of impact water vapor or gas emission in the form of H 2O, O 2 and H 2. The observations of the Cassini spac…
Stellar winds and mass loss from extreme helium stars
Hamann, W. -R.; Jeffery, C. S.
Extreme helium stars are very rare low-mass supergiants in a late stage of evolution. They are probably contracting to become white dwarfs following a violent phase of evolution which caused them to become hydrogen-deficient giants, possibly R CrB stars. Using the latest generation of models for spherically expanding stellar atmospheres, we set ou…
Gully formation on Mars: Two recent phases of formation suggested by links between morphology, slope orientation and insolation history
Head, James W.; Forget, François; Spiga, Aymeric +2 more
The unusual 80 km diameter Noachian-aged Asimov crater in Noachis Terra (46°S, 5°E) is characterized by extensive Noachian-Hesperian crater fill and a younger superposed annulus of valleys encircling the margins of the crater floor. These valleys provide an opportunity to study the relationships of gully geomorphology as a function of changing slo…
On the influence of non-thermal pressure on the mass determination of galaxy clusters
Laganá, T. F.; de Souza, R. S.; Keller, G. R.
Aims: Given that in most cases just thermal pressure is taken into account in the hydrostatic equilibrium equation to estimate galaxy cluster mass, the main purpose of this paper is to consider the contribution of all three non-thermal components to total mass measurements. The non-thermal pressure is composed by cosmic rays, turbulence and m…
Offset between dark matter and ordinary matter: evidence from a sample of 38 lensing clusters of galaxies
Zhao, Hongsheng; Shan, Huanyuan; Tao, Charling +3 more
We compile a sample of 38 galaxy clusters which have both X-ray and strong lensing observations, and study for each cluster the projected offset between the dominant component of baryonic matter centre (measured by X-rays) and the gravitational centre (measured by strong lensing). Among the total sample, 45 per cent clusters have offsets >10arc…
The Structure of the Accretion Disk in the Accretion Disk Corona X-ray Binary 4U 1822-371 at Optical and Ultraviolet Wavelengths
Cornell, Mark E.; Robinson, Edward L.; Hynes, Robert I. +2 more
The eclipsing low-mass X-ray binary 4U 1822-371 is the prototypical accretion disk corona (ADC) system. We have obtained new time-resolved UV spectroscopy of 4U 1822-371 with the Advanced Camera for Surveys/Solar Blind Channel on the Hubble Space Telescope and new V- and J-band photometry with the 1.3 m SMARTS telescope at Cerro Tololo Inter-Ameri…
The impact of a major cluster merger on galaxy evolution in MACSJ0025.4-1225
Schrabback, T.; Ebeling, H.; Ma, C. -J. +1 more
We present results of an extensive morphological, spectroscopic and photometric study of the galaxy population of MACSJ0025.4-1225 (z = 0.586), a major cluster merger with clear segregation of dark and luminous matter, to examine the impact of mergers on galaxy evolution. Based on 436 galaxy spectra obtained with Keck DEep Imaging Multi-Object Spe…
Constraints on Long-period Planets from an L'- and M-band Survey of Nearby Sun-like Stars: Observations
Heinze, A. N.; Kenworthy, Matthew; Sivanandam, Suresh +3 more
We present the observational results of an L'- and M-band adaptive optics imaging survey of 54 nearby, Sun-like stars for extrasolar planets, carried out using the Clio camera on the MMT. We have concentrated more strongly than all other planet-imaging surveys to date on very nearby F, G, and K stars, prioritizing stellar proximity higher than you…
Observational Aspects of the Three-dimensional Coronal Structure Over a Solar Activity Cycle
Morgan, Huw; Habbal, Shadia Rifai
Solar rotational tomography is applied to almost eleven years of Large Angle Spectrometric Coronagraph C2/Solar and Heliospheric Observatory data, revealing for the first time the behavior of the large-scale coronal density structures, also known as streamers, over almost a full solar activity cycle. This study gives an overview of the main result…
Puzzling asteroid 21 Lutetia: our knowledge prior to the Rosetta fly-by
Barucci, M. A.; Fornasier, S.; Fulchignoni, M. +5 more
Aims: A wide observational campaign was carried out in 2004-2009 that aimed to complete the ground-based investigation of Lutetia prior to the Rosetta fly-by in July 2010.
Methods: We obtained BVRI photometric and V-band polarimetric measurements over a wide range of phase angles, and visible and infrared spectra in the 0.4-2.4 µm …