Search

The VISCACHA (VIsible Soar photometry of star Clusters in tApii and Coxi HuguA†) Survey is an ongoing project based on deep and spatially resolved photometric observations of Magellanic Cloud star clusters, collected using the SOuthern Astrophysical Research (SOAR) telescope together with the SOAR Adaptive Module Imager. So far we have used >300h of telescope time to observe ∼150 star clusters, mostly with low mass (M < 104 M ⊙) on the outskirts of the LMC and SMC. With this high-quality data set, we homogeneously determine physical properties using deep colour-magnitude diagrams (ages, metallicities, reddening, distances, mass, luminosity and mass functions) and structural parameters (radial density profiles, sizes) for these clusters which are used as a proxy to investigate the interplay between the Magellanic Clouds and their evolution. We present the VISCACHA survey and its initial results, based on our first two papers. The project's long term goals and expected legacy to the community are also addressed. [ABSTRACT FROM AUTHOR]

Milky Way globular clusters are excellent laboratories for stellar population detailed analysis that can be applied to extragalactic environments with the advent of the 40m-class telescopes like the ELT. The globular cluster population traces the early evolution of the Milky Way which is the field of Galactic archaeology. We present our GlObular clusTer Homogeneous Abundance Measurement (GOTHAM) survey. We derived radial velocities, Teff, log(g), [Fe/H], [Mg/Fe] for red giant stars in one third of all Galactic globular clusters that represent well the Milky Way globular cluster system in terms of metallicity, mass, reddening, and distance. Our method is based on low-resolution spectroscopy and is intrinsically reddening free and efficient even for faint stars. Our [Fe/H] determinations agree with high-resolution results to within 0.08 dex. The GOTHAM survey provides a new metallicity scale for Galactic globular clusters with a significant update of metallicities higher than [Fe/H] > -0.7. We show that the trend of [Mg/Fe] with metallicity is not constant as previously found, because now we have more metal-rich clusters. Moreover, peculiar clusters whose [Mg/Fe] does not match Galactic stars for a given metallicity are discussed. We also measured the CaII triplet index for all stars and we show that the different chemical evolution of Milky Way open clusters, field stars, and globular clusters implies different calibrations of calcium triplet to metallicity. [ABSTRACT FROM AUTHOR]

The metallicity distribution and abundance ratios of the Galactic bulge are reviewed. Issues raised by different groups in recent work, in particular the high metallicity end, a comparison between the oxygen abundances derived from different indicators, the [OI] 630nm and IR OH lines, and the issue of measuring giants vs. dwarfs, are discussed. Finally, abundances in bulge globular clusters are briefly described. [ABSTRACT FROM PUBLISHER]

Division IV organizes astronomers studying the characterization, interior and atmospheric structure of stars of all masses, ages and chemical compositions. [ABSTRACT FROM PUBLISHER]

Stellar populations in the Milky Way and in external galaxies are reviewed, based on the conferences and posters presented at this meeting. [ABSTRACT FROM PUBLISHER]

The present study tries to identify the mechanism responsible for the hostility to star formation (SF) found in galaxies of dense environments. Among the several candidate mechanisms, the gas-rich merger of galaxies stands as a plausible option since the realisation that the AGN-feedback, which follows the merger, can deplete the gas and truncate the SF of the resulting spheroid. Our strategy is to look for traces of SF truncation in the elliptical galaxies of Hickson compact groups (HCGs), because these are the ideal environments for mergers to occur. The stellar populations of 22 elliptical galaxies in HCGs and 12 in the field are compared using three different SSP models and two different emission correction procedures. Along the study, an extensive use of the [Mg/Fe] abundance ratio is made, because it contains useful information on the timescale of the SF history of the galaxies. Systematic differences of [Mg/Fe] and [Z/H] between both galaxy subsamples (field and HCGs) suggest that SF truncation events have affected the intermediate-mass galaxies of the HCGs. Our interpretation is that when a field galaxy enters the dense HCG environment it merges with another galaxy and ends up as a passive elliptical with traces of SF truncation. [ABSTRACT FROM PUBLISHER]

We show that in a sample of Extremely Metal-Poor (EMP) giants (<[Fe/H]>=−3.1) all the stars with a luminosity higher than logL/L⊙ ≈ 2.6 present the characteristics of a mixing of the surface with the H-burning layer: low abundance of carbon and high abundance of nitrogen. In these “mixed stars” the lithium abundance and the ratio 12C/13C are very low. Some of these stars are also Na or/and Al rich. [ABSTRACT FROM PUBLISHER]

We present the distribution of Galactic bulge globular clusters and a method based on simultaneous detection of field and cluster horizontal branches to derive the cluster distances. This method has the advantage of being independent of both reddening and the reddening law, RV = AV/E(B−V). The vast majority of clusters projected in the direction of the Galactic bulge are located on the near side of the Galactic Center. Deviations from the reddening law do not seem to be responsible for this peculiarity. We need to introduce a peculiar, steep dependence of the absolute horizontal-branch magnitude with metallicity in the metal-rich regime if we want to reproduce a symmetrical distribution. Instead, if the observed distribution is correct, we expect a rather large number of bulge globular clusters are still to be discovered. [ABSTRACT FROM PUBLISHER]

The meeting of the Working Group on Active B-type Stars consisted of a business meeting followed by a scientific meeting containing invited and contributed talks. The titles of the talks and their presenters are listed below. We plan to publish a series of articles containing summaries of these talks in Issue No. 39 of the Be Star Newsletter. [ABSTRACT FROM PUBLISHER]

We analyze a sample of 21 super-metal-rich (SMR) stars, using high-resolution échelle spectra obtained with the FEROS Spectrograph at the 1.5m ESO telescope. The metallicities are in the range 0.15 < [Fe/H] < 0.5, 3 of them in common with Pompéia et al. (2002). Geneva photometry, astrometric data from Hipparcos, and radial velocities from CORAVEL are available for these stars. The peculiar kinematics suggests the thin disk close to the bulge as the probable birthplace of these stars (Grenon 1999). From Hipparcos data, it appears that the turnoff of this population indicates an age of 10-11 Gyr (Grenon 1999). Detailed analysis of the sample stars is carried out. Lithium abundances of these stars were derived, and their behaviour with effective temperature is shown. [ABSTRACT FROM PUBLISHER]

We analyze a sample of 21 super-metal-rich (SMR) stars, using high-resolution échelle spectra obtained with the Fiber-fed Extended Range Optical Spectrograph at the 1.5m ESO telescope. The metallicities are in the range 0.07 ≤ [Fe/H] ≤ 0.45, 3 of them in common with Pompéia et al. (2009). Geneva photometry, astrometric data from Hipparcos, and radial velocities from CORAVEL are available for these stars. The peculiar kinematics suggests the thin disk close to the bulge as the probable birthplace of these stars (Grenon 1999). From Hipparcos data, it appears that the turnoff of this population indicates an age of 10-11 Gyr (Grenon 1999). Detailed analysis of the sample stars is carried out, and atmospheric parameters are derived from spectroscopic and photometric determinations. Oxygen abundances of these stars are derived, and [O/Fe] overabundances up to +0.35 are found. [ABSTRACT FROM PUBLISHER]

Analysis of integrated spectra of star clusters in the Magellanic Clouds can bring important information for studies on the chemical evolution of the Clouds. The aim of the present work is to derive ages and metallicities from integrated spectra of 15 star clusters in the Small Magellanic Cloud (SMC), some of them not studied so far. Making use of a full spectrum fitting technique, we compared the integrated spectra of the sample clusters to three different sets of single stellar population models available in the literature. We derived ages and metallicities for the sample clusters employing the codes STARLIGHT and ULySS. Out of the 15 clusters in our sample, 9 are old/intermediate age clusters and 6 are young clusters. We point out the results for the newly identified as old/intermediate age clusters HW1, NGC 152, Lindsay 3 and 11. We also confirm old ages for NGC 361, NGC 419 and Kron 3, and the oldest well-known SMC cluster NGC 121. [ABSTRACT FROM PUBLISHER]

In this work we review the details, with emphasis on the near UV (3000-4500 Å), of the molecular database and the continuous opacity sources as implemented in the spectrum synthesis code used to calculate the spectral library presented in Coelho et al. (2005). We discuss our recent and future efforts towards the improvement of the calculation in this spectral range. [ABSTRACT FROM PUBLISHER]

The IAU Division IV (‘Stars’) organizes astronomers studying the characteristics, interior and atmospheric structure, and evolution of stars of all masses, ages, and chemical compositions.During the triennial starting at the Sydney General Assembly in August 2003, the following o.cials served in Division IV: President – Dainis Dravins (Lund, Sweden); Organizing Committee – Beatriz Barbuy (São Paolo, Brazil; former Div.IV president); Christopher Corbally (Vatican & Tucson, USA; Comm. 45 President); Wojciech Dziembowski (Warsaw, Poland; Comm. 35 President); William Hartkopf (Washington DC, USA; Comm. 26 President); Christopher Sneden (Austin, USA; Comm. 29 President), and Monique Spite (Paris-Meudon, France; Comm. 36 President). [ABSTRACT FROM PUBLISHER]

The Working Group Virtual Observatories, Data Centers, and Networks was established under Commission 5 at the Prague General Assembly in 2006. The purpose of the WG is to provide IAU oversight of the activities of the International Virtual Observatory Alliance (IVOA, ), to encourage data centers and other data providers to archive and publish data according to IVOA standards, and to help assure that astronomical research facilities are electronically linked with current network technologies. The WG coordinates activities closely with the WG-FITS, as the IVOA uses FITS as its primary format for binary data exchange, and the WG on Astronomical Data. [ABSTRACT FROM PUBLISHER]