EDP Sciences
Highlighted papers
The mysterious optical afterglow spectrum of GRB 140506A at z = 0.889 (Fynbo et al.)
Wednesday, 19 November 2014 08:00

Vol. 571
In section 6. Interstellar and circumstellar matter

The mysterious optical afterglow spectrum of GRB 140506A at z = 0.889

by J.P.U. Fynbo, T. Krühler, K. Leighly, et al. A&A 572, A12


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Gamma-ray bursts (GRBs) are powerful tools used to probe the interstellar medium of distant star-forming galaxies. The present work tries to clarify the mystery of the peculiar afterglow spectrum of the z = 0.889 GRB 140506A. Using spectroscopy with ESO/X-shooter at several epochs after the burst and imaging and spectroscopy of the host galaxy obtained with the Magellan telescope, the authors try to understand the origin of the very unusual properties of the absorption towards this GRB. It appears that there are several components aligned along the line of sight: first, a very broad and strong dust extinction in the visible associated with Balmer lines and variable between the two epochs; second, an HII region, detected with H and He excited absorption lines; third, a cooler region detected by molecular absorption from CH+. All three components have different velocities.

 
Eyes in the sky: Interactions between asymptotic giant branch [...] (van Marle et al.)
Monday, 03 November 2014 13:51

Vol. 571
In section 6. Interstellar and circumstellar matter

Eyes in the sky: Interactions between asymptotic giant branch star winds and the interstellar magnetic field

by A. J. van Marle, N. L. J. Cox, and L. Decin A&A 571, A131


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This is the most comprehensive study to date of the effects of weak magnetic fields on the expansion of evolved star winds. While the basic result is to be expected — that the interstellar magnetic field produces distinctly elongated, aspherical structures — the details are important for issues such as turbulence, shock structures, and transport of stellar nuclear products (hence mixing in the interstellar medium). The models are compared to Herschel images of wind-blown bubbles, but this will also be important for future missions, such as JWST, as well as for polarization studies.

 
The stripping of a galaxy group diving into the massive cluster A2142 (D. Eckert et al.)
Thursday, 30 October 2014 10:39

Vol. 570
In section 3. Cosmology

The stripping of a galaxy group diving into the massive cluster A2142

by D. Eckert, S. Molendi, M. Owers, et al. A&A 570, A119


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Large structures such as galaxy clusters form hierarchically in the universe by merging the subentities. Even though major mergers of clusters, like the bullet, are easy to see and study, and individual galaxies have also been frequently observed to fall inward and be stripped of gas in local clusters, such as Virgo or Coma, an infalling group is not very frequent. This work reports the discovery of a diffuse, irregular X-ray feature in the outskirts of the massive cluster Abell 2142, which is identified as an infalling galaxy group. The feature has a core-tail structure, where the core closer to the cluster center coincides with a group of galaxies. The tail pointing away from the cluster is 800kpc long, the longest X-ray tail ever reported. The gas of the tail is not as hot as the ambient X-ray gas, confirming it comes from a smaller structure. This is gas stripped from the infalling group. The 3D collisional velocity is approximately 1200 km/s. The survival of the tail in the hot X-ray medium of the cluster is 400 times longer than the conduction time scale. Conduction must be suppressed through a tangled magnetic field with a short coherence length and with plasma microinstabilities. With this long survival time, it is possible that the infalling material can eventually settle within the core of the main cluster.

 
Filamentary structure and Keplerian rotation in the high-mass star-forming [...] (Betran et al
Thursday, 06 November 2014 08:00

Vol. 571
In section 6. Interstellar and circumstellar matter

Filamentary structure and Keplerian rotation in the high-mass star-forming region G35.03+0.35 imaged with ALMA

by M.T. Beltran, A. Sanchez-Monge, R. Cesaroni, et al. A&A 571, A52


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Do massive stars form like low-mass stars? Massive stars play a fundamental role in the ecosystem of a galaxy, but because they are rare, little is known about the details of the their formation, at least in comparison to the formation of their lower mass siblings. Beltran et al. use ALMA observations of G35.03+0.35, the likely birth place of a B-type protostar, and find a filamentary structure fragmented into cores. One of them is core A, which harbors a hypercompact HII region. Position-velocity plots of the velocity gradient toward core A show clear signatures of Keplerian rotation and are consistent with the pattern of an edge-on Keplerian disk rotating about a star with a mass in the range 5–13 Msun. This result supports theoretical scenarios according to which high-mass stars, at least B-type stars, form through disk-mediated accretion.

 
Gaia-ESO analysis of UVES spectra of FGK-type stars (R. Smiljanic et al.)
Monday, 03 November 2014 09:36

Vol. 570
In section 8. Stellar atmospheres

The Gaia-ESO Survey: The analysis of high-resolution UVES spectra of FGK-type stars

by R. Smiljanic, A. J. Korn, M. Bergemann, et al. A&A 570, A122


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The Gaia-ESO Public Spectroscopic Survey will ultimately obtain high quality spectroscopic data for about 5 000 FGK-type stars using the FLAMES-UVES link at the VLT. This will be among the largest homogeneously analyzed samples of its kind. The extensive list of elemental abundances derived in these stars will enable significant advances in the areas of stellar evolution and Milky Way formation and evolution. In this paper, 1301 UVES spectra of Gaia benchmark stars and several stars clusters are analyzed in parallel with several different state-of-the-art methodologies. This paper presents these separate analyses and describes how the final recommended parameter scale is defined along with the precision and accuracy of the final parameters. These results are part of the Gaia-ESO second internal release and will be part of its first public release of advanced data products.

 
Planck 2013 results
Friday, 17 October 2014 09:27

Vol. 571

A&A special feature: Planck 2013 results

Planck Collaboration, A&A, volume 571, November 2014


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A&A press release. Astronomy & Astrophysics is publishing a special feature of 31 articles describing the data gathered by Planck over 15 months of observations and released by ESA and the Planck Collaboration in March 2013. This series of papers presents the initial scientific results extracted from this first Planck dataset. Read the A&A press release.

 

Editor-in-Chief: T. Forveille
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Managing Editor: C. Bertout

ISSN: 0004-6361 ; e-ISSN: 1432-0746
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Published by: EDP Sciences

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