Open clusters towards the Galactic centre: chemistry and dynamics

Magrini, L.; Randich, S.; Zoccali, M.; Jílková, Lucie; Carraro, G.; Galli, Daniele; Maiorca, E.; Busso, M.

doi:10.1051/0004-6361/201015395

Cited by 67 publications

(94 citation statements)

References 67 publications

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“…In F-, G-, and K-type stars whose photospheric continua are well-defined in high-resolution spectra, stellar metallicity is computed through spectral synthesis (McWilliam 1990;Valenti & Piskunov 1996;González 1997;González Hernández et al 2004;Valenti & Fischer 2005;Recio-Blanco et al 2006) or measuring equivalent widths, especially of iron lines (Sousa et al 2008(Sousa et al , 2011Magrini et al 2010;Adibekyan et al 2012;Tabernero et al 2012;Bensby et al 2014). However, it is not possible to measure a photospheric continuum in M-type stars and, thus, their metallicity is studied through other techniques.…”

Section: Metallicitymentioning

confidence: 99%

CARMENES input catalogue of M dwarfs

Alonso-Floriano¹,

Morales²,

Caballero³

et al. 2015

A&A

187

178

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Context. CARMENES is a stabilised, high-resolution, double-channel spectrograph at the 3.5 m Calar Alto telescope. It is optimally designed for radial-velocity surveys of M dwarfs with potentially habitable Earth-mass planets. Aims. We prepare a list of the brightest, single M dwarfs in each spectral subtype observable from the northern hemisphere, from which we will select the best planet-hunting targets for CARMENES. Methods. In this first paper on the preparation of our input catalogue, we compiled a large amount of public data and collected lowresolution optical spectroscopy with CAFOS at the 2.2 m Calar Alto telescope for 753 stars. We derived accurate spectral types using a dense grid of standard stars, a double least-squares minimisation technique, and 31 spectral indices previously defined by other authors. Additionally, we quantified surface gravity, metallicity, and chromospheric activity for all the stars in our sample. Results. We calculated spectral types for all 753 stars, of which 305 are new and 448 are revised. We measured pseudo-equivalent widths of Hα for all the stars in our sample, concluded that chromospheric activity does not affect spectral typing from our indices, and tabulated 49 stars that had been reported to be young stars in open clusters, moving groups, and stellar associations. Of the 753 stars, two are new subdwarf candidates, three are T Tauri stars, 25 are giants, 44 are K dwarfs, and 679 are M dwarfs. Many of the 261 investigated dwarfs in the range M4.0-8.0 V are among the brightest stars known in their spectral subtype. Conclusions. This collection of low-resolution spectroscopic data serves as a candidate target list for the CARMENES survey and can be highly valuable for other radial-velocity surveys of M dwarfs and for studies of cool dwarfs in the solar neighbourhood.

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Section: Metallicitymentioning

confidence: 99%

CARMENES input catalogue of M dwarfs

Alonso-Floriano¹,

Morales²,

Caballero³

et al. 2015

A&A

187

178

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“…The five youngest clusters with ages from 10 to 100 Myr serve as an illustrative example of spread in [Fe/H] (Friel et al 2002(Friel et al , 2010Magrini et al 2010). Frinchaboy et al (2013) have presented chemical abundances of 28 OCs derived from the automated processing of infrared spectra of cluster giants collected from the APOGEE survey in the tenth data release of the Sloan Digital Sky Survey (SDSS-III, DR10; Ahn et al 2014).…”

Section: Age-metallicity Relationmentioning

confidence: 99%

The evolution of the Milky Way: new insights from open clusters

Reddy¹,

Lambert²,

Giridhar³

2016

Mon. Not. R. Astron. Soc.

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We have collected high-dispersion echelle spectra of red giant members in the twelve open clusters (OCs) and derived stellar parameters and chemical abundances for 26 species by either line equivalent widths or synthetic spectrum analyses. We confirm the lack of an age−metallicity relation for OCs but argue that such a lack of trend for OCs arise from the limited coverage in metallicity compared to that of field stars which span a wide range in metallicity and age. We confirm that the radial metallicity gradient of OCs is steeper (flatter) for R gc < 12 kpc (>12 kpc). We demonstrate that the sample of clusters constituting a steep radial metallicity gradient of slope −0.052±0.011 dex kpc −1 at R gc < 12 kpc are younger than 1.5 Gyr and located close to the Galactic midplane (| z| < 0.5 kpc) with kinematics typical of the thin disc. Whereas the clusters describing a shallow slope of −0.015±0.007 dex kpc −1 at R gc > 12 kpc are relatively old, thick disc members with a striking spread in age and height above the midplane (0.5 < | z| < 2.5 kpc). Our investigation reveals that the OCs and field stars yield consistent radial metallicity gradients if the comparison is limited to samples drawn from the similar vertical heights. We argue via the computation of Galactic orbits that all the outer disc clusters were actually born inward of 12 kpc but the orbital eccentricity has taken them to present locations very far from their birthplaces.

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“…Finally, we calculated the Galactic orbit of each star adopting a gravitational potential including the bar, deriving estimates for the eccentricity (e), the apo-and perigalacticon (R a and R p ), and the absolute value of the maximum height above the plane Z max , which are also indicated in Table 7. Orbits were computed following the method described in Magrini et al (2010) and Jilkova et al (in prep. ), which the reader is referred to for details.…”

Section: Thick-disk Membershipmentioning

confidence: 99%

Lithium-rich giants in the Galactic thick disk

Monaco

Villanova

Bidin

et al. 2011

A&A

Self Cite

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Context. Lithium is a fragile element, which is easily destroyed in the stellar interior. The existence of lithium-rich giants still represents a challenge for stellar evolution models. Aims. We have collected a large database of high-resolution stellar spectra of 824 candidate thick-disk giants having 2 MASS photometry and proper motions measured by the Southern Proper-Motion Program (SPM). In order to investigate the nature of Li-rich giants, we searched this database for giants presenting a strong Li I resonance line. Methods. We performed a chemical abundance analysis on the selected stars with the MOOG code along with proper ATLAS-9 model atmospheres. The iron content and atmospheric parameters were fixed by using the equivalent width of a sample of Fe lines. We also derive abundances for C, N, and O and measure or derive lower limits on the 12 C/ 13 C isotopic ratios, which is a sensible diagnostic of the stars evolutionary status. Results. We detected five stars with a lithium abundance higher than 1.5, i.e. Li-rich according to the current definition. One of them (SPM-313132) has A(Li) > 3.3 and, because of this, belongs to the group of the rare super Li-rich giants. Its kinematics makes it a likely thin-disk member and its atmospheric parameters are compatible with it being a 4 M star either on the red giant branch (RGB) or the early asymptotic giant branch. This object is the first super Li-rich giant detected at this phase. The other four are likely low-mass thick-disk stars evolved past the RGB luminosity bump, as determined from their metallicities and atmospheric parameters. The most evolved of them lies close to the RGB-tip. It has A(Li) > 2.7 and a low 12 C/ 13 C isotopic ratio, close to the cool bottom processing predictions.

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Open clusters towards the Galactic centre: chemistry and dynamics

Cited by 67 publications

References 67 publications

CARMENES input catalogue of M dwarfs

CARMENES input catalogue of M dwarfs

The evolution of the Milky Way: new insights from open clusters

Lithium-rich giants in the Galactic thick disk

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