Search Publications
INTEGRAL Spectral Variability Study of the Atoll 4U 1820-30: First Detection of Hard X-Ray Emission
Ubertini, P.; Bazzano, A.; Tarana, A. +1 more
We study the 4-200 keV spectral and temporal behavior of the low-mass X-ray binary 4U 1820-30 with INTEGRAL during 2003-2005. This source as been observed in both the soft (banana) and hard (island) spectral states. A high-energy tail, above 50 keV, in the hard state has been observed for the first time. This places the source in the category of X…
The relative timing of supra-arcade downflows in solar flares
Fletcher, L.; Bain, H. M.; Khan, J. I.
Context: Supra-arcade downflows (generally dark, sunward-propagating features located above the bright arcade of loops in some solar flares) have been reported mostly during the decay phase, although some have also been reported during the rise phase of solar flares.
Aims: We investigate, from a statistical point of view, the timing of supra-a…
Composition of the atmosphere of Venus below the clouds
Bézard, Bruno; de Bergh, Catherine
The composition of Venus' lower atmosphere, beneath the clouds, has been investigated through both in situ measurements and remote-sensing observations. In 1978 the mass spectrometers and gas chromatographs aboard the Venera 11-12 landers and Pioneer Venus Large probe returned unique information on the abundances of carbon dioxide, nitrogen, noble…
The dark haloes of early-type galaxies in low-density environments: XMM-Newton and Chandra observations of NGC 57, 7796 and IC 1531
Ponman, Trevor J.; O'Sullivan, Ewan; Sanderson, Alastair J. R.
We present analysis of Chandra and XMM-Newton observations of three early-type galaxies, NGC 57, 7796 and IC 1531. All three are found in very low-density environments, and appear to have no neighbours of comparable size. NGC 57 has a halo of kT ~ 0.9 keV, solar metallicity gas, while NGC 7796 and IC 1531 both have ~0.55 keV, 0.5-0.6Zsolar
Vertical sheets of dense plasma in the topside Martian ionosphere
Gurnett, D. A.; Wang, X. -D.; Orosei, R. +6 more
The low-frequency radar, Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), on board the Mars Express spacecraft is used to sound electron densities in the topside Martian ionosphere. The radar records the delay times to echoes of reflected radio waves as a function of frequency, yielding spectrograms with traces of radar echoes.…
Suzaku Observation of Diffuse X-Ray Emission from the Carina Nebula
Hamaguchi, Kenji; Petre, Robert; Tsujimoto, Masahiro +9 more
We studied extended X-ray emission from the Carina Nebula taken with the Suzaku CCD camera XIS on 2005 August 29.The X-ray morphology, plasma temperature, and absorption to the plasma are consistent with the earlier Einstein results.The Suzaku spectra newly revealed emission lines from various species, including oxygen, but not from nitrogen.This …
Magnetic Field Properties of Flux Cancellation Sites
Kubo, M.; Shimizu, T.
It has been frequently observed in longitudinal magnetograms that magnetic elements disappear when a magnetic polarity element approaches and collides with another polarity element. We examine 12 collision events observed with the Advanced Stokes Polarimeter. We find formation of new magnetic connection between the colliding opposite polarity elem…
Velocities and divergences as a function of supergranule size
Roudier, Th.; Meunier, N.; Rieutord, M. +1 more
Context: The origin of supergranulation is not understood yet and many scenarios, which range from large-scale deep convection to large-scale instabilities of surface granular flows, are possible.
Aims: We characterize the velocities and divergences in supergranulation cells as a function of their size.
Methods: Using local correlation tra…
Evolution of Field Spiral Galaxies up to Redshifts z = 1
Böhm, Asmus; Ziegler, Bodo L.
We have gained intermediate-resolution spectroscopy with the FORS instruments of the Very Large Telescope (VLT) and high-resolution imaging with the Advanced Camera for Surveys aboard HST for a sample of 220 distant field spiral galaxies within the FORS Deep Field and William Herschel Deep Field. Spatially resolved rotation curves were extracted a…
Comparison of plasma data from ASPERA-3/Mars-Express with a 3-D hybrid simulation
Barabash, S.; Lundin, R.; Krupp, N. +8 more
The ELS and IMA sensors of the ASPERA-3 experiment onboard of Mars-Express (MEX) can measure electron as well as ion moments. We compare these measurements for a specific orbit with the simulation results from a 3-D hybrid model. In the hybrid approximation the electrons are modeled as a massless charge-neutralizing fluid, whereas the ions are tre…