Brown Dwarfs in the Pleiades Cluster Confirmed by the Lithium Test

Реболо, Р.; Martín, E. L.; Basri, Gibor; Marcy, Geoffrey W.; Osorio, M. R. Zapatero

doi:10.1086/310263

Cited by 190 publications

(135 citation statements)

References 23 publications

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“…Rapid mixing in these fully-convective stars then leads to complete Li destruction throughout the star on a time scale that is short compared with their contraction time scales (e.g. Basri, Marcy & Graham 1996;Rebolo et al 1996;Bildsten et al 1997). The time it takes to reach this Li-burning threshold increases with decreasing stellar mass.…”

Section: Introductionmentioning

confidence: 99%

The effect of star-spots on the ages of low-mass stars determined from the lithium depletion boundary

Jackson

Jeffries

2014

Monthly Notices of the Royal Astronomical Society

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In a coeval group of low-mass stars, the luminosity of the sharp transition between stars that retain their initial lithium and those at slightly higher masses in which Li has been depleted by nuclear reactions, the lithium depletion boundary (LDB), has been advanced as an almost model-independent means of establishing an age scale for young stars. Here we construct polytropic models of contracting pre-main sequence stars (PMS) that have cool, magnetic starspots blocking a fraction β of their photospheric flux. Starspots slow the descent along Hayashi tracks, leading to lower core temperatures and less Li destruction at a given mass and age. The age, τ LDB , determined from the luminosity of the LDB, L LDB , is increased by a factor (1 − β) −E compared to that inferred from unspotted models, where E ≃ 1 + d log τ LDB /d log L LDB and has a value ∼ 0.5 at ages < 80 Myr, decreasing to ∼ 0.3 for older stars. Spotted stars have virtually the same relationship between K-band bolometric correction and colour as unspotted stars, so this relationship applies equally to ages inferred from the absolute K magnitude of the LDB. Low-mass PMS stars do have starspots, but the appropriate value of β is highly uncertain with a probable range of 0.1 < β < 0.4. For the smaller β values our result suggests a modest systematic increase in LDB ages that is comparable with the maximum levels of theoretical uncertainty previously claimed for the technique. The largest β values would however increase LDB ages by 20-30 per cent and demand a re-evaluation of other age estimation techniques calibrated using LDB ages.

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Section: Introductionmentioning

confidence: 99%

The effect of star-spots on the ages of low-mass stars determined from the lithium depletion boundary

Jackson

Jeffries

2014

Monthly Notices of the Royal Astronomical Society

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“…This technique, the so-called lithium depletion boundary method Rebolo et al 1996;Stauffer et al 1998;Barrado y Navascués et al 1999), does however have both merits and limitations. Line strengths and elemental abundance ratios are fairly straight forward to measure, and are indeed fundamental stellar properties, perhaps more so than compared to magnetic activity indicators.…”

Section: Introductionmentioning

confidence: 99%

New rotation periods in the open cluster NGC 1039 (M 34), and a derivation of its gyrochronology age

James

Barnes

Meibom

et al. 2010

A&A

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Aims. Employing photometric rotation periods for solar-type stars in NGC 1039 [M 34], a young, nearby open cluster, we use its mass-dependent rotation period distribution to derive the cluster's age in a distance independent way, i.e., the so-called gyrochronology method. Methods. We present an analysis of 55 new rotation periods, using light curves derived from differential photometry, for solar type stars in the open cluster NGC 1039 [M 34]. We also exploit the results of a recently-completed, standardized, homogeneous BV Ic CCD survey of the cluster, performed by the Indiana Group of the WIYN open cluster survey, in order to establish photometric cluster membership and assign B − V colours to each photometric variable. We describe a methodology for establishing the gyrochronology age for an ensemble of solar-type stars. Empirical relations between rotation period, photometric colour and stellar age (gyrochronology) are used to determine the age of M 34. Based on its position in a colour-period diagram, each M 34 member is designated as being either a solid-body rotator (interface or I-star), a differentially rotating star (convective or C-star) or an object which is in some transitory state in between the two (gap or g-star). Fitting the period and photometric colour of each I-sequence star in the cluster, we derive the cluster's mean gyrochronology age. Results. Of the photometric variable stars in the cluster field, for which we derive a period, 47 out of 55 of them lie along the loci of the cluster main sequence in V/B − V and V/V − I space. We are further able to confirm kinematic membership of the cluster for half of the periodic variables [21/55], employing results from an on-going radial velocity survey of the cluster. For each cluster member identified as an I-sequence object in the colour-period diagram, we derive its individual gyrochronology age, where the mean gyro age of M 34 is found to be 193 ± 9 Myr. Conclusions. Using differential photometry, members of a young open cluster can be easily identified in a colour−magnitude diagram from their periodic photometric variability alone. Such periodicity can be used to establish a period-colour distribution for the cluster, which for M 34, we have used to derive its gyrochronology age of 193 ± 9 Myr. Formally, our gyro age of M 34 is consistent (within the errors) with that derived using several distance-dependent, photometric isochrone methods (250 ± 67 Myr).

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“…At later times, 7 Li is continuously produced by stellar nucleosynthesis (Travaglio et al 2001), as well as by spallation and α + α fusion reactions of Galactic cosmicrays (GCRs) interacting with the interstellar medium (ISM), while 6 Li is almost purely synthesized by the GCR-ISM interactions (Meneguzzi et al 1971;Prantzos et al 1993;Ramaty et al 1997). Both 6 Li and 7 Li have a destruction sink of stellar processing once they are embedded in the stellar envelope and interior where they are easily burnt at T ∼ 10 6 K. This fragile nature of lithium in turn provides a critical test in identifying brown dwarfs (Rebolo et al 1996) and planet harboring stars (Israelian et al 2001). Detection of lithium in primeval gas from the big bang and in various stellar objects provides important keys to understanding not only the origin of atomic nuclides but the chemical evolution of stars and galaxies.…”

Section: Introductionmentioning

confidence: 99%

THE NEW DETECTIONS OF⁷Li/⁶Li ISOTOPIC RATIO IN THE INTERSTELLAR MEDIA

Kawanomoto

Kajino

Aoki

et al. 2009

ApJ

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We have determined the isotopic abundance ratio of 7 Li/ 6 Li in the interstellar media (ISMs) along lines of sight to HD169454 and HD250290 using the High-Dispersion Spectrograph on the Subaru Telescope. We also observed ζ Oph for comparison with previous data. The observed abundance ratios were 7 Li/ 6 Li = 8.1 +3.6 −1.8 and 6.3 +3.0 −1.7 for HD169454 and HD250290, respectively. These values are in reasonable agreement with those observed previously in the solar neighborhood ISMs within ±2σ error bars and are also consistent with our measurement of 7 Li/ 6 Li = 7.1 +2.9 −1.6 for a cloud along the line of sight to ζ Oph. This is good evidence for homogeneous mixing and instantaneous recycling of the gas component in the Galactic disk. We also discuss several source compositions of 7 Li, Galactic cosmic-ray interactions, stellar nucleosynthesis, and big bang nucleosynthesis.

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Brown Dwarfs in the Pleiades Cluster Confirmed by the Lithium Test

Cited by 190 publications

References 23 publications

The effect of star-spots on the ages of low-mass stars determined from the lithium depletion boundary

The effect of star-spots on the ages of low-mass stars determined from the lithium depletion boundary

New rotation periods in the open cluster NGC 1039 (M 34), and a derivation of its gyrochronology age

THE NEW DETECTIONS OF⁷Li/⁶Li ISOTOPIC RATIO IN THE INTERSTELLAR MEDIA

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Brown Dwarfs in the Pleiades Cluster Confirmed by the Lithium Test

Cited by 190 publications

References 23 publications

The effect of star-spots on the ages of low-mass stars determined from the lithium depletion boundary

The effect of star-spots on the ages of low-mass stars determined from the lithium depletion boundary

New rotation periods in the open cluster NGC 1039 (M 34), and a derivation of its gyrochronology age

THE NEW DETECTIONS OF7Li/6Li ISOTOPIC RATIO IN THE INTERSTELLAR MEDIA

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THE NEW DETECTIONS OF⁷Li/⁶Li ISOTOPIC RATIO IN THE INTERSTELLAR MEDIA