Ground-based CCD astrometry with wide-field imagers

Yadav, R. K. S.; Bedin, Luigi R.; Piotto, G.; Anderson, Jay; Cassisi, S.; Villanova, S.; Platais, I.; Pasquini, L.; Momany, Y.; Sagar, Ram

doi:10.1051/0004-6361:20079245

Cited by 131 publications

(228 citation statements)

References 48 publications

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“…Barycentric radial velocities were determined from the individual spectra yielding a radial velocity of −33.8 ± 0.4 km s −1 . This is in exellent agreement (1σ) with the mean radial velocity of the cluster as determined by Pasquini et al (2008), v rad = −33.30 ± 0.40, and Yadav et al (2008), v rad = −33.673 ± 0.208. The latter study classifies M67-1194 as a high-probability proper-motion cluster member (99%).…”

Section: Observationssupporting

confidence: 84%

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M67-1194, an unusually Sun-like solar twin in M67

Önehag

Korn

Gustafsson

et al. 2011

A&A

100

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Context. The rich open cluster M67 is known to have a chemical composition close to solar, and an age around 4 Gyr. It thus offers the opportunity to check our understanding of the physics and the evolution of solar-type stars in a cluster environment. Aims. We present the first spectroscopic study at high resolution, R ≈ 50 000, of the potentially best solar twin, M67-1194, identified among solar-like stars in M67. Methods. G dwarfs in M67 (d ≈ 900 pc) are relatively faint (V ≈ 15), which makes detailed spectroscopic studies time-consuming. Based on a pre-selection of solar-twin candidates performed at medium resolution by Pasquini et al. (2008, A&A, 489, 677), we explore the chemical-abundance similarities and differences between M67-1194 and the Sun, using VLT/FLAMES-UVES. Working with a solar twin in the framework of a differential analysis, we minimize systematic model errors in the abundance analysis compared to previous studies which utilized more evolved stars to determine the metallicity of M67. The differential approach yields precise and accurate chemical abundances for M67, which enhances the possibility to use this object in studies of the potential peculiarity, or normality, of the Sun. Results. We find M67-1194 to have stellar parameters indistinguishable from the solar values, with the exception of the overall metallicity which is slightly super-solar ([Fe/H] = 0.023 ± 0.015). An age determination based on evolutionary tracks yields 4.2 ± 1.6 Gyr. Most surprisingly, we find the chemical abundance pattern to closely resemble the solar one, in contrast to most known solar twins in the solar neighbourhood. Conclusions. We confirm the solar-twin nature of M67-1194, the first solar twin known to belong to a stellar association. This fact allows us to put some constraints on the physical reasons for the seemingly systematic departure of M67-1194 and the Sun from most known solar twins regarding chemical composition. We find that radiative dust cleansing by nearby luminous stars may be the explanation for the peculiar composition of both the Sun and M67-1194, but alternative explanations are also possible. The chemical similarity between the Sun and M67-1194 also suggests that the Sun once formed in a cluster like M67.

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Section: Observationssupporting

confidence: 84%

“…Its age is also comparable to that of the Sun: 3.5-4.8 Gyr (e.g. Yadav et al 2008). M67 is relatively nearby (∼900 pc) and is only little affected by interstellar extinction, which allows detailed spectroscopic studies of its main-sequence stars.…”

Section: Introductionmentioning

confidence: 97%

M67-1194, an unusually Sun-like solar twin in M67

Önehag

Korn

Gustafsson

et al. 2011

A&A

100

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“…[Fe/H] = 0.01, (m− M) = 9.68, and E(B−V) = 0.02, and age of 3.87 Gyr. Black dots are the stars from the sample of Yadav et al (2008), red filled circles are the stars studied in this paper, and open squares are deviant stars (see Sect. 5.3).…”

Section: Sample and Datamentioning

confidence: 99%

Lithium in M 67: From the main sequence to the red giant branch

Pace

Castro

Meléndez

et al. 2012

A&A

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Context.Lithium abundances in open clusters are a very effective probe of mixing processes, and their study can help us to understand the large depletion of lithium that occurs in the Sun. Owing to its age and metallicity, the open cluster M 67 is especially interesting on this respect. Many studies of lithium abundances in M 67 have been performed, but a homogeneous global analysis of lithium in stars from subsolar masses and extending to the most massive members, has yet to be accomplished for a large sample based on high-quality spectra. Aims. We test our non-standard models, which were calibrated using the Sun with observational data. Methods.We collect literature data to analyze, for the first time in a homogeneous way, the non-local thermal equilibrium lithium abundances of all observed single stars in M 67 more massive than ∼0.9 M . Our grid of evolutionary models is computed assuming a non-standard mixing at metallicity [Fe/H] = 0.01, using the Toulouse-Geneva evolution code. Our analysis starts from the entrance into the zero-age main-sequence. Results. Lithium in M 67 is a tight function of mass for stars more massive than the Sun, apart from a few outliers. A plateau in lithium abundances is observed for turn-off stars. Both less massive (M ≤ 1.10 M ) and more massive (M ≥ 1.28 M ) stars are more depleted than those in the plateau. There is a significant scatter in lithium abundances for any given mass M ≤ 1.1 M . Conclusions. Our models qualitatively reproduce most of the features described above, although the predicted depletion of lithium is 0.45 dex smaller than observed for masses in the plateau region, i.e. between 1.1 and 1.28 solar masses. More work is clearly needed to accurately reproduce the observations. Despite hints that chromospheric activity and rotation play a role in lithium depletion, no firm conclusion can be drawn with the presently available data.

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“…Since, OCLs are embedded in the Galactic disk and are generally affected by the field star contamination, hence it is necessary to distinguish between members and non-members in the field of cluster. In recent years, the detailed membership analysis of stars in the cluster field has become a subject of intense investigation, mainly in view to understand the cluster properties (Carraro et al, 2008;Yadav et al, 2008;Joshi et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Basic parameters of open star clusters DOLIDZE 14 and NGC 110 in infrared bands

Joshi

et al. 2015

New Astronomy

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The basic physical parameters of a poorly studied open cluster NGC 110 and an unstudied open cluster DOLIDZE 14 are estimated in the present study using the archival P P MXL and W ISE catalogues. The radius of both the clusters are estimated by fitting the modified King's empirical model on their stellar density profiles. The other basic parameters of the clusters such as distance, reddening, and age are obtained by visual fitting of the Marigo's solar metallicity isochrone on their IR colour-magnitude diagrams (CMDs). The mean-proper motion of the clusters are estimated through the individual proper motion of probable members identified through the dynamical and statistical methods. The archival catalogues (JHKW 1 W 2 ) are constructed for both the clusters by compiling the extracted data from the P P MXL and W ISE catalogues. The various colour-excesses, such as E(J −H), E(H −K) and E(W 1 − W 2 ), are estimated using the best fit theoretical isochrone on the (J − H) − H, (H − K) − H and (W 1 − W 2 ) − H CMDs, respectively. The ratios of various infrared colours of the clusters are obtained through their two-colour diagrams. We also identify the most probable members in these clusters by estimating spatial, kinematic and spatio-kinematic probabilities of stars within the cluster. A correlation between the E(H −K) and E(W 1 −W 2 ) is also established.

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Ground-based CCD astrometry with wide-field imagers

Cited by 131 publications

References 48 publications

M67-1194, an unusually Sun-like solar twin in M67

M67-1194, an unusually Sun-like solar twin in M67

Lithium in M 67: From the main sequence to the red giant branch

Basic parameters of open star clusters DOLIDZE 14 and NGC 110 in infrared bands

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