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Ca II triplet spectroscopy has been used to derive stellar metallicities for individual stars in four LMC fields situated at galactocentric distances of 3\arcdeg, 5\arcdeg, 6\arcdeg\@ and 8\arcdeg\@ to the north of the Bar. Observed…

Astrophysics · Physics 2009-11-13 Ricardo Carrera , Carme Gallart , Eduardo Hardy , Antonio Aparicio , Robert Zinn

Stellar evolution models which include the effect of helium and heavy element diffusion have been calculated for initial iron abundances of [Fe/H] = -2.3, -2.1, -1.9 and -1.7. These models were calculated for a large variety of masses and…

Astrophysics · Physics 2011-02-11 Brian Chaboyer , W. H. Fenton , Jenica E. Nelan , D. J. Patnaude , Francesca E. Simon

Asteroseismic parameters allow us to measure the basic stellar properties of field giants observed far across the Galaxy. Most of such determinations are, up to now, based on simple scaling relations involving the large frequency…

Ages have been derived for 55 globular clusters (GCs) from overlays of isochrones onto the turnoff photometry, assuming distances based on fits of zero-age horizontal branch (ZAHB) models to the lower bound of the observed distributions of…

Astrophysics of Galaxies · Physics 2013-10-14 Don A. Vandenberg , Karsten Brogaard , Ryan Leaman , Luca Casagrande

We provide detailed abundance analyses of 8 candidate super-metal-rich stars. Five of them are confirmed to have [Fe/H] > 0.2 dex, the generally-accepted limit for super-metal-richness. Furthermore, we derive abundances of several elements…

Astrophysics · Physics 2007-05-23 Sofia Feltzing , Guillermo Gonzalez

We present the results of a study of young unresolved stellar groupings (clusters, OB associations, and their complexes) associated with HII regions, based on the coupling of spectroscopic, photometric and H{\alpha} spectrophotometric…

Astrophysics of Galaxies · Physics 2023-07-13 A. S. Gusev , F. Sakhibov , O. V. Egorov , V. S. Kostiuk , E. V. Shimanovskaya

Large numbers of low-to-medium resolution spectra of M-type dwarf stars from both the local Galactic disk and halo are available from various surveys. In order to fully exploit these data, we develop a template-fit method using a set of…

Solar and Stellar Astrophysics · Physics 2020-03-11 Neda Hejazi , Sebastien Lepine , Derek Homeier , R. Michael Rich , Michael M. Shara

We performed a uniform and detailed analysis of 1112 high-resolution spectra of FGK dwarfs obtained with the HARPS spectrograph at the ESO 3.6 m telescope (La Silla, Chile). Most stars have effective temperatures 4700 K < Teff < 6300 K and…

Astrophysics of Galaxies · Physics 2011-11-22 V. Zh. Adibekyan , N. C. Santos , S. G. Sousa , G. Israelian

We study 147 star clusters in the Large Magellanic Cloud (LMC) in order to determine their mean metallicities and ages, as well as the mean metallicities of 80 surrounding fields. We construct an age-metallicity relation (AMR) for the…

We present a detailed analysis of the star formation history (SFH) of three fields in M33 located ~ 4 - 6 visual scale lengths from its nucleus. These fields were imaged with the Advanced Camera for Surveys on the Hubble Space Telescope and…

Astrophysics · Physics 2008-11-26 Michael K. Barker , Ata Sarajedini , Doug Geisler , Paul Harding , Robert Schommer

We present equivalent widths, improved model atmosphere parameters, and revised abundances for 14 species of 11 elements derived from high resolution optical spectroscopy of 311 metal-poor stars. All of these stars had their parameters…

Solar and Stellar Astrophysics · Physics 2025-02-27 Sanil Mittal , Ian U. Roederer

We present B, V, R, and H alpha photometry of 8 clusters in the Small Magellanic Cloud, 5 in the Large Magellanic Cloud, and 3 Galactic clusters, and use 2 color diagrams (2-CDs) to identify candidate Be star populations in these clusters.…

Astrophysics · Physics 2011-02-11 John P. Wisniewski , Karen S. Bjorkman , ;

We present the parameters of 891 stars, mostly clump giants, including atmospheric parameters, distances, absolute magnitudes, spatial velocities, galactic orbits and ages. One part of this sample consists of local giants, within 100 pc,…

Astrophysics · Physics 2009-11-13 C. Soubiran , O. Bienayme , T. V. Mishenina , V. V. Kovtyukh

For the first time, the abundances of a large sample of subgiant and turn-off region stars in omega Centauri have been measured, the data base being medium resolution spectroscopy from FORS2 at the VLT. Absolute iron abundances were derived…

Astrophysics · Physics 2009-11-10 Michael Hilker , Andrea Kayser , Tom Richtler , Philip Willemsen

Given the massive spectroscopic surveys and the Gaia mission, the Milky Way has turned into a unique laboratory to be explored using abundance ratios that show a strong dependency with time. Within this framework, the data provided through…

We derive age-metallicity relations (AMRs) and orbital parameters for the 1658 solar neighbourhood stars to which accurate distances are measured by the HIPPARCOS satellite. The sample stars comprise 1382 thin disc stars, 229 thick disc…

Astrophysics · Physics 2009-11-07 A. Ibukiyama , N. Arimoto

We explore the possible evolutionary status of the primary component of the binary 85 Pegasi, listed as a target for asteroseismic observations by the MOST satellite. In spite of the assessed `subdwarf' status, and of the accurate distance…

Astrophysics · Physics 2009-11-13 F. D'Antona , D. Cardini , M. P. Di Mauro , C. Maceroni , I. Mazzitelli , J. Montalban

We briefly review the main features in the broad-band colour evolution of star clusters, over the complete age interval from 10^7 to 10^(10) yr. The emphasis is in the problem of age-dating distant young clusters (<2 Gyr) from their…

Astrophysics · Physics 2007-05-23 Leo Girardi

The recent Gaia Data Release 1 of stellar parallaxes provides ample opportunity to find metal-poor main-sequence stars with precise parallaxes. We select 21 such stars with parallax uncertainties better than $\sigma_\pi/\pi\leq0.10$ and…

Solar and Stellar Astrophysics · Physics 2017-04-12 Erin M. O'Malley , Christina Gilligan , Brian Chaboyer
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