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Time Scales for CA II Emission Decay, Rotational Braking, and Lithium Depletion
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1972
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Ca II emission luminosity, corrected for spectral‑type effects, declines with age as the inverse square root across the Pleiades, Ursa Major, Hyades, and the Sun. Because Ca II emission scales linearly with surface magnetic field, which in turn tracks stellar angular velocity, the magnetic field—and thus the emission—decays as the inverse square root of age. The study finds that stellar rotational decay follows the same inverse‑square‑root law, lithium depletion matches this law only up to the Hyades age (~0.4 Gyr) before becoming exponential, and these results hinge on the adopted Hyades age. Published in The Astrophysical Journal, February 1972 (DOI 10.1086/151310).
view Abstract Citations (1668) References (8) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Time Scales for Ca II Emission Decay, Rotational Braking, and Lithium Depletion Skumanich, A. Abstract A comparison of the Ca+ emission luminosity-after correction for spectral-type effects-for the Pleiades, Ursa Major, and Hyades stars and the Sun indicate an emission decay which varies as the inverse square root of the age. Further, the rotational decay curve is found to satisfy the same law. It is further suggested that lithium depletion follows the same law but only as far as the Hyades age, after which the depletion proceeds exponentially. Since Ca+ emission is linearly proportional to magnetic field strength at the surface, one can predict that the surface fields are proportional to angular velocity and decay as the inverse square root. The above results are predicated Qi' the standard Hyades age (0.4 billion years). Publication: The Astrophysical Journal Pub Date: February 1972 DOI: 10.1086/151310 Bibcode: 1972ApJ...171..565S full text sources ADS | data products SIMBAD (4)