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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.

 
Dynamical star-disk interaction in the young stellar system V354 Mon (Fonseca et al.)
Monday, 07 July 2014 11:35

Vol. 567
In section 7. Stellar structure and evolution

Dynamical star-disk interaction in the young stellar system V354 Monocerotis

by N.N.J. Fonseca, S.H.P. Alencar, J. Bouvier, et al. A&A 567, A39


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The light curve of the classical T Tauri star V354 Mon shows periodical minima that vary in depth and width at each rotational cycle. The photometric observations carried out by the authors indicate that the system becomes slightly bluer as the flux increases. The spectra obtained by the authors exhibit variable emission lines, with redshifted absorption components associated with a disk wind and blueshifted ones with the accretion process, which confirms the magnetospheric accretion scenario. From the analysis of the photometric and spectroscopic data, the authors identify correlations between the emission line variability and the light-curve modulation of the young system, such as the occurrence of pronounced redshifted absorption in the Hα line at the epoch of minimum flux. The authors find that the accretion funnel is seen projected onto the stellar photosphere along the line of sight, which implies that the hot spot coincides with the light-curve minima. They conclude that material non-uniformly distributed in the inner part of the circumstellar disk is the main cause of the photometric modulation, but do not exclude that there might be hot and cold spots at the stellar surface. The distortion in the inner part of the disk is thought to be created by the dynamical interaction between the stellar magnetosphere and the circumstellar disk, as also observed in the T Tauri star AA Tau and predicted by magneto-hydrodynamical numerical simulations.

 
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.

 
Grain growth in the envelopes and disks of Class I protostars (Miotello et al.)
Monday, 07 July 2014 08:28

Vol. 567
In section 6. Interstellar and circumstellar matter

Grain growth in the envelopes and disks of Class I protostars

by A. Miotello, L. Testi, G. Lodato, L. Ricci, G. Rosotti, K. Brooks, A. Maury, and A. Natta, A&A 567, A32


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The authors present new 3 mm ATCA data of two Class I young stellar objects, Elias29 and WL12, which are expected to be surrounded by both an extended envelope and a disk. In the (u, v) plane the two sources present a similar behavior. First, there is a nearly constant emission at long baselines, which suggests the presence of an unresolved component. Second, the fluxes increase at short baselines, indicating the presence of an extended envelope. Our data analysis leads to unusually low values of the spectral index, which indicates that mm-sized dust grains have already formed at this early stage both in the envelopes and in the central, compact disk-like structures. This result may provide new constraints for the initial dust evolution in protoplanetary disks.

 

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

Mirror sites: CDS | EDP Sciences
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