Search Publications
Vertical profiling of SO 2 and SO above Venus' clouds by SPICAV/SOIR solar occultations
Montmessin, Franck; Belyaev, Denis A.; Fedorova, Anna A. +6 more
New measurements of sulfur dioxide (SO 2) and monoxide (SO) in the atmosphere of Venus by SPICAV/SOIR instrument onboard Venus Express orbiter provide ample statistics to study the behavior of these gases above Venus' clouds. The instrument (a set of three spectrometers) is capable to sound atmospheric structure above the clouds in seve…
Black Hole Powered Nebulae and a Case Study of the Ultraluminous X-Ray Source IC 342 X-1
Feng, Hua; Grisé, Fabien; Kaaret, Philip +6 more
We present new radio, optical, and X-ray observations of three ultraluminous X-ray sources (ULXs) that are associated with large-scale nebulae. We report the discovery of a radio nebula associated with the ULX IC 342 X-1 using the Very Large Array (VLA). Complementary VLA observations of the nebula around Holmberg II X-1, and high-frequency Austra…
Modelling the huge, Herschel-resolved debris ring around HD 207129
Magain, P.; Krivov, A. V.; Eiroa, C. +18 more
Debris disks, which are inferred from the observed infrared excess to be ensembles of dust, rocks, and probably planetesimals, are common features of stellar systems. As the mechanisms of their formation and evolution are linked to those of planetary bodies, they provide valuable information. The few well-resolved debris disks are even more valuab…
Orion revisited. I. The massive cluster in front of the Orion nebula cluster
Bouy, H.; Alves, J.
Aims: The aim of this work is to characterize the stellar population between Earth and the Orion A molecular cloud where the well-known star formation benchmark Orion nebula cluster (ONC) is embedded.
Methods: We used the denser regions the Orion A cloud to block optical background light, effectively isolating the stellar population in f…
Interstellar H I and H2 in the Magellanic Clouds: An Expanded Sample Based on Ultraviolet Absorption-line Data
Welty, Daniel E.; Wong, Tony; Xue, Rui
We have determined column densities of H I and/or H2 for sight lines in the Magellanic Clouds from archival Hubble Space Telescope and Far-Ultraviolet Spectroscopic Explorer spectra of H I Lyα and H2 Lyman-band absorption. Together with some similar data from the literature, we now have absorption-based N(H I) and/or N(H…
Titan’s internal structure and the evolutionary consequences
Fortes, A. D.
Titan’s moment of inertia (MoI), estimated from the quadrupole gravity field measured by the Cassini spacecraft, is 0.342, which has been interpreted as evidence of a partially differentiated internal mass distribution. It is shown here that the observed MoI is equally consistent with a fully differentiated internal structure comprising a shell of…
Two Extrasolar Asteroids with Low Volatile-element Mass Fractions
Koester, D.; Zuckerman, B.; Xu, S. +2 more
Using ultraviolet spectra obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope, we extend our previous ground-based optical determinations of the composition of the extrasolar asteroids accreted onto two white dwarfs, GD 40 and G241-6. Combining optical and ultraviolet spectra of these stars with He-dominated atmospheres, 13…
Dynamics of the Solar Magnetic Bright Points Derived from Their Horizontal Motions
Chitta, L. P.; Kariyappa, R.; van Ballegooijen, A. A. +2 more
The subarcsecond bright points (BPs) associated with the small-scale magnetic fields in the lower solar atmosphere are advected by the evolution of the photospheric granules. We measure various quantities related to the horizontal motions of the BPs observed in two wavelengths, including the velocity autocorrelation function. A 1 hr time sequence …
Active upper-atmosphere chemistry and dynamics from polar circulation reversal on Titan
Vinatier, Sandrine; Nixon, Conor A.; Irwin, Patrick G. J. +6 more
Saturn's moon Titan has a nitrogen atmosphere comparable to Earth's, with a surface pressure of 1.4 bar. Numerical models reproduce the tropospheric conditions very well but have trouble explaining the observed middle-atmosphere temperatures, composition and winds. The top of the middle-atmosphere circulation has been thought to lie at an altitude…
AKARI observations of ice absorption bands towards edge-on young stellar objects
Tamura, M.; Kandori, R.; Pontoppidan, K. M. +9 more
Context. Circumstellar disks and envelopes of low-mass young stellar objects (YSOs) contain significant amounts of ice. Such icy material will evolve to become volatile components of planetary systems, such as comets in our solar system.
Aims: To investigate the composition and evolution of circumstellar ice around low-mass young stellar obje…