ARCHEOLOGY OF AN ANCIENT STAR

We report on the bright and late F-type star HR 3138, which, with respect to its chemistry in the [Mg/H]-[Fe/Mg] abundance plane, we identify as an old Population II member. Evolutionary tracks are, however, in conflict with this finding and instead imply an age of only [tau] = 5.6 super(-1.8) sub(+...

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Bibliographic Details
Published in:The Astrophysical journal 2012-12, Vol.761 (2), p.1-8
Main Authors: FUHRMANN, K, CHINI, R, HAAS, M, HACKSTEIN, M, RAMOLLA, M, BERNKOPF, J
Format: Article
Language:English
Subjects:
Accretion
ACCURACY
Astronomy
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
CHEMISTRY
Clouds
Earth, ocean, space
ELEMENT ABUNDANCE
Exact sciences and technology
FRICTION
IRON
LITHIUM
MAGNESIUM
MASS
Open clusters
PHOTOSPHERE
Progenitors (astrophysics)
RADIAL VELOCITY
STAR ACCRETION
STAR CLUSTERS
STAR EVOLUTION
Stars
WHITE DWARF STARS
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Summary:We report on the bright and late F-type star HR 3138, which, with respect to its chemistry in the [Mg/H]-[Fe/Mg] abundance plane, we identify as an old Population II member. Evolutionary tracks are, however, in conflict with this finding and instead imply an age of only [tau] = 5.6 super(-1.8) sub(+2.2) Gyr (2[sigma]) for HR 3138. We discuss this controversy in light of existing high-precision radial velocity surveys that mostly exclude the case of a blue straggler primary and a white dwarf secondary. While it is realized that a stellar merger can principally solve the issue and there is indeed observational evidence for mass accretion on HR 3138 from the absence of lithium in its photosphere, we also consider the interesting circumstance that HR 3138 lies in the direction to the 350 pc distant, young open cluster NGC 2516. We point to the possibility that the progenitor cloud of this cluster may likewise account for former mass accretion and we argue in particular for a dynamical friction with this cloud as a plausible cause for the strikingly common Galactic rotational velocity of the field star and open cluster.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/761/2/159