Lithium in M67

Hobbs, L. M.; Pilachowski, Catherine A.

doi:10.1086/184794

Cited by 45 publications

(26 citation statements)

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“…While the Li line strength becomes weaker as a star gets older, an EW of lithium is also strongly dependent on stellar colors (or mass) by the different depths of the outer convective cells and by different amounts of angular momentum. This is shown in the top panel of Figure 15 Butler et al 1987;Soderblom et al 1993;Garcia Lopez et al 1994;Jones et al 1996;Jeffries 1999), the Hyades (black open box; Soderblom et al 1990Soderblom et al , 1995Thorburn et al 1993), and M67 (open diamond; Hobbs & Pilachowski 1986;Spite et al 1987;Garcia Lopez et al 1988;Pasquini et al 1997;Jones et al 1999;Randich et al 2002) at the age of 100Myr, 550Myr, and 4 Gyr, respectively. On top of these, our KPNO sample stars are marked by red closed circles.…”

Section: Lithium Absorptionsmentioning

confidence: 93%

Spectroscopic Survey of G and K Dwarfs in the Hipparcos Catalog. I. Comparison Between the Hipparcos and Photometric Parallaxes

Kim

Stauffer

et al. 2016

ApJS

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The tension between the Hipparcos parallax of the Pleiades and other independent distance estimates continues even after the new reduction of the Hipparcos astrometric data and the development of a new geometric distance measurement for the cluster. A short Pleiades distance from the Hipparcos parallax predicts a number of stars in the solar neighborhood that are sub-luminous at a given photospheric abundance. We test this hypothesis using the spectroscopic abundances for a subset of stars in the Hipparcos catalog, which occupy the same region as the Pleiades in the color-magnitude diagram. We derive stellar parameters for 170 nearby G-and K-type field dwarfs in the Hipparcos catalog based on high-resolution spectra obtained using KPNO 4 m echelle spectrograph. Our analysis shows that, when the Hipparcos parallaxes are adopted, most of our sample stars follow empirical colormagnitude relations. A small fraction of stars are too faint compared to main-sequence fitting relations bymag, but the differences are marginal at a 2s level, partly due to relatively large parallax errors. On the other hand, we find that the photometric distances of stars showing signatures of youth as determined from lithium absorption line strengths and R HK ¢ chromospheric activity indices are consistent with the Hipparcos parallaxes. Our result is contradictory to a suggestion that the Pleiades distance from main-sequence fitting is significantly altered by stellar activity and/or the young age of its stars, and provides an additional supporting evidence for the longdistance scale of the Pleiades.

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Section: Lithium Absorptionsmentioning

confidence: 93%

Spectroscopic Survey of G and K Dwarfs in the Hipparcos Catalog. I. Comparison Between the Hipparcos and Photometric Parallaxes

Kim

Stauffer

et al. 2016

ApJS

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“…Initial studies included the Hyades and Praesepe at ages of about 600 Myr (e.g. Wallerstein, Herbig & Conti 1963;Boesgaard & Tripicco 1986;Boesgaard & Budge 1988;Soderblom et al 1990), NGC 752 (age 1.7 Gyr, Hobbs & Pilachowski 1986a) and M67 (age 4 Gyr, Hobbs & Pilachowski 1986b). These studies, which were focused on stars at the solar T eff and hotter, immediately revealed what has been termed the "F-star Li gap".…”

Section: In Older Post-zams Clustersmentioning

confidence: 99%

Using rotation, magnetic activity and lithium to estimate the ages of low mass stars

Jeffries

2014

EAS Publications Series

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Abstract. The rotation rate, level of magnetic activity and surface lithium abundance are age-dependent quantities in stars of about a solar mass and below. The physical reasons for the evolution of these phenomena are qualitatively understood, but accurate quantitative models remain dependent on empirical calibration using the Sun and stars of known age, chiefly in clusters. In this work I review the status of these "empirical age indicators", outlining the astrophysics of their time dependence, describing the measurements, assessing the precision (and accuracy) of age estimates when applied to individual stars, and identifying their principle limitations in terms of the mass and age ranges over which they are useful. Finally, I discuss the "lithium depletion boundary" technique which, in contrast to the empirical methods, appears to provide robust, almost model-independent ages that are both precise and accurate, but which is only applicable to coeval groups of stars.

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“…For the solar twin YBP 1194, Önehag et al (2011) used the highest quality spectra available to date to determine its lithium abundance, although their result is essentially identical with that of Castro et al (2011), which is based on lower quality spectra; thus, either of the sources can be adopted to measure the lithium abundance of YBP 1194. The data in Pasquini et al (1997), Garcia Lopez et al (1988), Spite et al (1987), and Hobbs & Pilachowski (1986) were initially considered for the present compilation but eventually not used, since their whole sample was later reanalyzed in some of the works cited above. We also did not include in our compilation data from Deliyannis et al (1994), which is a study of tidally locked binaries, whose mechanism of lithium depletion may completely differ from that of single stars.…”

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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Lithium in M67

Cited by 45 publications

References 0 publications

Spectroscopic Survey of G and K Dwarfs in the Hipparcos Catalog. I. Comparison Between the Hipparcos and Photometric Parallaxes

Spectroscopic Survey of G and K Dwarfs in the Hipparcos Catalog. I. Comparison Between the Hipparcos and Photometric Parallaxes

Using rotation, magnetic activity and lithium to estimate the ages of low mass stars

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

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