Rotation, Lithium Abundance and Chromospheric Emission in M34 Members

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Session 22 -- Stellar Spectroscopy, Atmospheres, Models, Intrinsic Variables, Theory, Part II
Display presentation, Tuesday, June 13, 1995, 9:20am - 6:30pm

[22.18] Rotation, Lithium Abundance and Chromospheric Emission in M34 Members

D. Fischer, B.F. Jones, M.D. Shetrone (Lick Observatory), Soderblom, D.R. (STScI)

As part of our ongoing program to study Li abundance in stars of known ages, we have obtained high-resolution echelle spectra for 41 members of the open cluster M34 using the Keck telescope.

We use these spectra to derive rotational velocities (vsini), and equivalent widths of Li, H $\alpha$ and the Ca II infrared triplet lines in order to assess the correlation of rotation, Li abundance and chromospheric activity with age.

The observations of M34 members are compared with previous observations of Pleides and Hyades members. M34 ($\approx 200 Myr$) is intermediate in age between the Pleides ( $\approx 65 Myr$) and the Hyades ($\approx 800 Myr$). Previous observations have demonstrated a wide range in rotation among late-G and K dwarfs in the Pleides. By contrast, stars of a similar spectral type in the Hyades show little variation in their rotation rates. This suggests that convergence in rotation rates among stars of a particular spectral type is an evolutionary effect. Previous observations have also indicated a correlation between rotation and chromospheric activity in Pleides stars. Another difference between the Pleides and Hyades clusters has been in the measured lithium abundance for stars of a particular effective temperature. The Pleides stars show a large degree of scatter while the Hyades stars show little difference in lithium abundance.

The observations of stars in M34 provide a check on the correlation of these features with age. Like the Pleides, the M34 members show a dispersion in Li abundance among low mass stars and also a substantial spread in rotational velocities.

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