EDP Sciences
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Highlighted papers
TANAMI monitoring of Centaurus A (Müller et al.)
Wednesday, 01 October 2014 08:00

Vol. 569
In section 10. Planets and planetary systems

TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet

by C. Müller, M. Kadler, R. Ojha, et al. A&A 569, A115


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VLBI monitoring has revealed striking structures on subparsec scales in the radio jet of Centaurus A (Cen A). The proper motions over 3.5 years of individual jet components have been followed every six months at 8.4 GHz with the Australian Long Baseline Array (LBA) and associated telescopes in Antarctica, Chile, New Zealand and South Africa, complemented by quasi-simultaneous 22.3 GHz observations. They show apparent component speeds within 0.1c to 0.3c, with some varying higher speed differential motions superposed on a long-term stable feature. The interpretation is in terms of a spine-sheath structure with a faster inner jet and downstream acceleration where the jet becomes optically thin. The flow appears to be interrupted by an obstacle causing a local decrease in surface brightness and circumfluent jet behavior. A jet-star interaction could explain these features.

 
Joint cosmological analysis of the SNLS and SDSS SNe Ia (Betoule et al.)
Friday, 08 August 2014 08:00

Vol. 568
In section 3. Cosmology

Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples

by M Betoule, R. Kessler, J. Guy, J. Mosher, D. Hardin, et al. A&A 568, A22


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In recent years we have discovered not onlythat the Universe expands, but that it also does so in an accelerating manner. The physical cause of this acceleration is rather uncertain and it has been attributed to either a peculiar fluid, called dark energy, or to a possible gravity modification to be introduced in Einstein's general relativity field equations. To make progress on this key cosmological problem, cosmologists use a specific type (the so-called Type Ia) of distant supernovae to precisely map the distance-redshift relation up to very large distances, thereby tracking the late-time expansion history of the Universe. This paper presents results from the latest version of this experiment by combining a recently acquired sample of 740 supernovae with high-quality light curves.

 
The Mice at play in the CALIFA survey (Wild et al.)
Monday, 28 July 2014 10:58

Vol. 567
In section 4. Extragalactic astronomy

The Mice at play in the CALIFA survey: A case study of a gas-rich major merger between first passage and coalescence

by V. Wild, F. Rosales-Ortega, J. Falcon-Barroso, et al. A&A 567, A132


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New optical 3D-spectroscopy of the Mice, an ongoing merger between two massive gas-rich spirals, provides better knowledge of stellar and gas kinematics, ionized gas properties, and stellar population diagnostics, with 1.6 kpc spatial resolution. Although the merger-induced star formation has not yet contributed significantly to the stellar mass of the galaxies, the impact of the galaxy interaction is already important: distortions and twists of the stellar and ionized gas disk, induced formation of strong bars, and gas streaming motions. In addition, both galaxies show bicones of high-ionization gas extending along their minor axes. This corresponds to nuclear gas outflows, which are superwinds driven by either the starburst or the active galaxy nuclei (Seyfert-like), proving that feedback is in action.

 
KIC10553698: An sdBV+WD binary (R. H. Østensen et al.)
Wednesday, 10 September 2014 12:49

Vol. 568
In section 7. Stellar structure and evolution

Asteroseismology revealing trapped modes in KIC 10553698A

by R. H. Ostensen, J. H. Telting, M. D. Reed, A. S. Baran, P. Nemeth, and F. Kiaeerad A&A 568, A15


Most hot subdwarf-B (sdB) stars belong to the population of extreme-horizontal-branch (EHB) stars. Several binary scenarios have been identified that can produce EHB stars, including either common-envelope ejection or stable Roche-lobe overflow. The sdBs pulsate with short (p modes) and long periods (g modes) because of the iron-group elements opacity bump (kappa mechanism). A key element in driving pulsations in sdBs is the competition between radiative levitation and gravitational settling, which causes a local overabundance of iron in the driving zone. KIC 10553698A is one of 16 sdBs observed with one-minute sampling rate for most of the duration of the Kepler mission. The authors identify the rich g-mode pulsation modes as components of rotationally split multiplets in a star rotating with a period of ~41 d. They are able to detect for the first time l = 1 modes that interpose in the asymptotic period sequences and that provide a clear indication of mode trapping in a stratified envelope, as predicted by theoretical models. A clear periodicity is also present in the Kepler photometry at 3.387 d. Spectroscopic observations reveal a radial-velocity amplitude of 64.8 km/s, indicating that the companion must be a white dwarf with a mass close to 0.6 M_o.

 
X-Shooter study of accretion and winds in transitional disks (Manara et al.)
Thursday, 07 August 2014 08:00

Vol. 568
In section 6. Interstellar and circumstellar matter

Gas content of transitional disks: a VLT/X-Shooter study of accretion and winds

by C. F. Manara, L. Testi, A. Natta, G. Rosotti, M. Benisty, B. Ercolano, and L. Ricci A&A 568, A18


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Transitional disks are thought to be a late evolutionary stage of protoplanetary disks whose inner regions have been depleted of dust. Using X-Shooter broad band - UV to NIR - medium-resolution spectroscopy, the authors derive the stellar, accretion, and wind properties of a sample of 22 transitional disks chosen among the largest accretors. The analysis of these properties allows the authors to constrain the gas content in a region very close to the star (≲ 0.2 AU) that is not accessible with any other observational technique. They find that the accretion rates and wind properties of 80% of the transitional disks in their sample are comparable to those of classical T Tauri stars. These results suggest that there is a gas-rich inner disk in these strongly accreting transitional disks with a density similar to that of classical T Tauri disks, even though the dust has been cleared from that same region.

 
Effect of rotational mixing and metallicity on hot star wind mass-loss rates (Krticka et al
Thursday, 10 July 2014 08:00

Vol. 567
In section 7. Stellar structure and evolution

Effect of rotational mixing and metallicity on the hot star wind mass-loss rates

by J. Krticka and J. Kubat A&A 567, A63


The metallicity dependence of the mass loss rate of hot stars is often described as scaling with the overall metallicity. The authors look into the impact of CNO processed material on the mass loss rate. Their calculations show that while it has small effect for solar metallicity stars, it can have important consequences for metal-poor stars.

 

Editor-in-Chief: T. Forveille
Letters Editor-in-Chief: J. Alves
Managing Editor: C. Bertout

ISSN: 0004-6361 ; e-ISSN: 1432-0746
Frequency: 12 volumes per year
Published by: EDP Sciences

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