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.   Improved photometric calibration of the SNLS and the SDSS supernova surveys (Betoule et al.) Monday, 15 April 2013 09:00 Vol. 552 In section 13. Astronomical instrumentation Improved photometric calibration of the SNLS and the SDSS supernova surveys by M. Betoule, J. Marriner, N. Regnault, et al. A&A 552, A124 Substantial efforts over the past few years have brought the photometric calibration accuracy of some large imaging surveys down to the 1% or 2% level. This already impressive level, however, remains a limiting factor in some uses of those surveys, including the measurement of precise cosmological parameters from the Hubble diagram of type Ia supernovae. The authors have used multiple overlapping calibration paths to both cross-calibrate large sets of tertiary standard stars in the fields of the Supernovae Legacy Survey (SNLS) and SDSS supernovae searches and calibrate those standards onto the scale of the HST primary photometric standards. The resulting photometry is calibrated to the HST system with 0.4% accuracy, which is comparable to the external accuracy of the HST primary standards.   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   A candidate circumbinary Keplerian disk in G35.20-0.74N: A study with ALMA (Sanchez-Monge et al.) Friday, 12 April 2013 09:15 Vol. 552 In section 1. Letters A candidate circumbinary Keplerian disk in G35.20-0.74N: A study with ALMA by A. Sanchez-Monge, R. Cesaroni, M.T. Beltran, et al. A&A 552, L10 The authors report on ALMA observations of continuum and molecular line emission with 0.′′4 resolution towards the high-mass star-forming region G35.20­0.74 N. Two dense cores are detected in typical hot-core tracers, such as CH3CN, and they reveal velocity gradients. In one of these cores, the velocity field can be fitted with an almost edge-on Keplerian disk rotating about a central mass of ~ 18 solar masses.