Three-dimensional orbits of the triple-O stellar system HD 150136 (H. Sana et al.) Friday, 24 May 2013 08:47 Vol. 553 In section 7. Stellar structure and evolution Three-dimensional orbits of the triple-O stellar system HD 150136 by H. Sana, J.-B. Le Bouquin, L. Mahy, O. Absil, M. De Becker, and E. Gosset A&A 553, A131 Direct mass estimates of high-mass stars are rare. The authors combine spectroscopic and interferometric observations to determine the orbits and masses of the three components of the triple-O star HD150136. This is the first direct measurement of the mass of an O3 star - an important reference point to test the evolution of massive stars. Although the error bars are still relatively high, they could be reduced by further monitoring of the system.   Migration and azimuthal variations (P. Di Matteo et al.) Thursday, 16 May 2013 08:00 Vol. 553 In section 5. Galactic Structure, stellar clusters and population Signatures of radial migration in barred galaxies: Azimuthal variations in the metallicity distribution of old stars by P. Di Matteo, M. Haywood, F. Combes, B. Semelin, and O. N. Snaith A&A 553, A102 The authors used N-body simulations to show that radial migration of stars in a galaxy disk, which are induced by a bar and spiral arms, can lead to significant azimuthal variation in the metallicity distribution of old stars at various distances from the center of a galaxy. These variations are predicted to be most visible when the bar is strongest, and they will diminish as the bar fades. Once the migration finishes up, then the mixing processes will start to smooth the disk out once again. These simulations thus suggest that the presence of inhomogeneities in the metallicity distribution of older stars in the disk of a barred galaxy can be used to as a probe of ongoing stellar migration within the disk. These signatures may be observable in the Milky Way by GAIA and related spectroscopic surveys. They should also be visible in external galaxies in the detailed IFU observations of stellar disks.   The dust of RZ Psc (W. J. de Wit et al.) Friday, 26 April 2013 08:56 Vol. 553 In section 1. Letters Active asteroid belt causes the UXOR phenomenon in RZ Piscium by W.J. de Wit, V .P. Grinin, I.S. Potravnov, D.N. Shakhovskoi, A. Mueller, and M. Moerchen A&A 553, L1 RZ Psc is a solar-type K0IV star well known for its variability, which is similar to the so-called UXOR variability seen in pre-main sequence stars and is attributed to the occultation by optically thick dust in stars with circumstellar disks. However, with an inferred age of 30 Ma, RZ Psc is relatively old compared to the usual UXOR-variable stars. de Wit et al. use infrared data (from WISE, IRAS, AKARI, and 2MASS) and visible photometric observation from the past 40 years to understand what this object is made of. The spectral energy distribution has a very significant excess that corresponds to a well-defined blackbody temperature of 500K. The photometric data show a 12.4-year period and very pronounced minima at random times. The authors interpret these as evidence for an optically thick dust ring around 0.7 AU and a substellar ("planet") companion at an orbital distance of 5.3 AU that apparently perturbs/wraps this ring and causes it to partially occult the star. The authors propose that the sharp photometric minima might be caused by the collision of planetesimals; which would produce an estimated 1e20 g of dust (equivalent to a full 20 km radius object reduced to dust). While these results have to be put to the test (observationally and theoretically), they show that RZ Psc is indeed an intriguing object that could help us understand disk evolution and planet formation.   Towards a resolved Kennicutt-Schmidt law at high redshift (J. Freundlich et al.) Friday, 24 May 2013 12:27 Vol. 552 In section 4. Extragalactic astronomy Towards a resolved Kennicutt-Schmidt law at high redshift by J. Freundlich, F. Combes, L. J. Tacconi, et al. A&A 553, A130 Understanding star formation in the distant Universe is one of the major challenges in present-day observational astronomy. In this paper the authors present the results of a detailed study using observations from the IRAM Plateau de Bure interferometer and the Keck DEEP2 spectroscopic survey of four massive star-forming galaxies at z~1.2. Resolving the individual star-forming regions in these galaxies is impossible, but combining optical spectroscopy with CO observations enables the determination of both the gas and the star formation surface densities of ensembles of clumps that constitute galaxies at these high redshifts. The integrated CO line luminosity is directly proportional to the total gas mass, and the star formation rate is deduced from the [OII] recombination line. The authors thus derive a spatially resolved Kennicutt-Schmidt relation for a scale of -8 kpc in each of these galaxies. The data indicate that the average time it will take for each galaxy to use up all its gas will be around 1.9 Gyr, but there are large variations in this value within each galaxy.   Direct-imaging of a 12–14 MJup object orbiting a M-dwarf binary system (Delorme et al.) Monday, 22 April 2013 14:28 Vol. 553 In section 1. Letters Direct-imaging discovery of a 12–14 Jupiter-mass object orbiting a young binary system of very low-mass stars by P. Delorme, J. Gagné, J. H. Girard, et al. A&A 553, L5 The discovery of exoplanets by direct imaging is particularly interesting given the possibility of then directly characterizing these systems by spectroscopy and studying their orbit, etc. With this article, Delorme et al. present the discovery of a planet or brown-dwarf about 13 times the mass of Jupiter. A number of similar exoplanets have been detected by imaging, but the particularity is that it orbits a pair of low-mass stars (about 0.2 solar masses) instead of a single star. With a projected orbital distance of 82AU, a distance to the Earth of only 47 pc, and an age estimated at only 30 Myr, this is a system that will be extremely interesting to follow and study, in particular to determine whether this object formed as a planet or as a brown dwarf. Its name, 2MASS J01033563-5515561(AB)b, may be difficult to remember so the author proposes nicknaming it 2MASS0103(AB)b.   Spatial distribution of water in the stratosphere of Jupiter [...] (Cavalié et al.) Tuesday, 23 April 2013 08:00 Vol. 553 In section 10. Planets and planetary systems Spatial distribution of water in the stratosphere of Jupiter from Herschel HIFI and PACS observations by T. Cavalié, H. Feuchtgruber, E. Lellouch, et al. A&A 553, A21 A&A press release: Astronomy & Astrophysics is publishing Herschel observations of water in Jupiter’s stratosphere. It is a clear remnant of the Shoemaker-Levy 9 impact on Jupiter nearly twenty years ago. Read the A&A press release