Search Publications
Neptune's cloud and haze variations 1994-2008 from 500 HST-WFPC2 images
Karkoschka, Erich
The analysis of all suitable images taken of Neptune with the Wide Field Planetary Camera 2 on the Hubble Space Telescope between 1994 and 2008 revealed the following results. The activity of discrete cloud features located near Neptune's tropopause remained roughly constant within each year but changed significantly on the time scale of ∼5 years.…
Extended X-Ray Emission in the Vicinity of the Microquasar LS 5039: Pulsar Wind Nebula?
Pavlov, George G.; Kargaltsev, Oleg; Garmire, Gordon P. +2 more
LS 5039 is a high-mass binary with a period of 4 days, containing a compact object and an O-star, one of the few high-mass binaries detected in γ-rays. Our Chandra Advanced CCD Imaging Spectrometer observation of LS 5039 provided a high-significance (≈10σ) detection of extended emission clearly visible for up to 1' from the point source. The spect…
The fundamental parameters of the roAp star γ Equulei
Chesneau, O.; Goldfinger, P. J.; Sturmann, J. +18 more
Context. A precise comparison of the predicted and observed locations of stars in the H-R diagram is needed when testing stellar interior theoretical models. For doing this, one must rely on accurate, observed stellar fundamental parameters (mass, radius, luminosity, and abundances).
Aims: We determine the angular diameter of the rapidly osci…
Constructing and Characterising Solar Structure Models for Computational Helioseismology
Moradi, H.; Gizon, L.; Schunker, H. +1 more
In local helioseismology, numerical simulations of wave propagation are useful to model the interaction of solar waves with perturbations to a background solar model. However, the solution to the linearised equations of motion include convective modes that can swamp the helioseismic waves that we are interested in. In this article, we construct ba…
Sulfuric acid aerosols in the atmospheres of the terrestrial planets
Grinspoon, David H.; Toon, Owen B.; McGouldrick, Kevin
Clouds and hazes composed of sulfuric acid are observed to exist or postulated to have once existed on each of the terrestrial planets with atmospheres in our solar system. Venus today maintains a global cover of clouds composed of a sulfuric acid/water solution that extends in altitude from roughly 50 km to roughly 80 km. Terrestrial polar strato…
Simulating the one-dimensional structure of Titan's upper atmosphere: 3. Mechanisms determining methane escape
Bar-Nun, Akiva; Bougher, Stephen W.; Mandt, Kathleen E. +11 more
This investigation extends the work presented by Bell et al. (2010a, 2010b). Using the one-dimensional (1-D) configuration of the Titan Global Ionosphere-Thermosphere Model (T-GITM), we quantify the relative importance of the different dynamical and chemical mechanisms that determine the CH4 escape rates calculated by T-GITM. Moreover, …
The (sub-)millimeter SED of protoplanetary disks in the outskirts of the Orion nebula cluster
Robberto, M.; Testi, L.; Natta, A. +5 more
We present the sub-mm/mm SED for a sample of eight young circumstellar disks in the outer regions of the Orion nebula cluster (ONC). New observations were carried out at 2.9 mm with the CARMA array and for one disk, 216-0939, at 3.3 and 6.8 mm with ATCA. By combining these new millimeter data with literature measurements at sub-millimeter waveleng…
Discovery of the X-ray selected galaxy cluster XMMU J0338.8+0021 at z = 1.49. Indications of a young system with a brightest galaxy in formation
Böhringer, H.; Rosati, P.; Šuhada, R. +11 more
We report the discovery of a galaxy cluster at z = 1.490 originally selected as an extended X-ray source in the XMM-Newton Distant Cluster Project. Further observations carried out with the VLT-FORS2 spectrograph allowed the spectroscopic confirmation of seven secure cluster members, providing a median system redshift of z = 1.490 ± 0.009. The col…
First hyperfine resolved far-infrared OH spectrum from a star-forming region
van Dishoeck, E. F.; Bergin, E. A.; Goicoechea, J. R. +9 more
OH is an important molecule in the H2O chemistry and the cooling budget of star-forming regions. The goal of the Herschel key program "Water In Star-forming regions with Herschel" (WISH) is to study H2O and related species during protostellar evolution. Our aim in this Letter is to assess the origin of the OH emission from st…
The quasar PG 0844+349 in an X-ray weak state
Schartel, N.; Fabian, A. C.; Komossa, S. +4 more
In 2009 March the well-studied quasar, PG 0844+349, was discovered with Swift to be in an X-ray weak state. A follow-up XMM-Newton observation several weeks later generated a good-quality spectrum of the source, showing substantial curvature and spectral hardening. In combination with archival data at two previous epochs when the source was in a b…