Spectroscopic Abundances of Solar-Type Dwarfs in the Open Cluster M34 (NGC 1039)The Astronomical Journal
PublisherThe American Astronomical Society
AbstractParameters and relative abundances of Fe, Ni, Ti, Cr, Ca, Si, Al, and Mg have been derived for nine M34 G and K dwarfs from high-resolution, modest signal-to-noise ratio Keck HIRES spectra. Eﬀective temperatures have been derived spectroscopically and fall in the range 4750 K Teﬀ 6130 K. Despite modest scatter in Fe, Ti, Cr, Ca, Al, and Mg (none of which is found to be correlated with Li scatter in M34), our two coolest stars are slightly though consistently underabundant in these elements relative to the warmer stars. The two cool stars are slightly overabundant in Si, whose abundances are derived from higher excitation lines. This and our ﬁnding that Fe ii–based abundances are signiﬁcantly higher than Fe i–based values in the cool stars seem to point toward the action of non-LTE eﬀects (overionization, overexcitation, or both), though additional analysis is required to exclude inadequacies in the model atmospheres. Final mean cluster abundances are based on ﬁve warm stars, which indicate [Fe/H] = +0.07 Æ0.04, and are void of any statistically signiﬁcant scatter. The other elements scale well with Fe except for Ni, which appears to be slightly underabundant with respect to Fe. Potassium abundances are derived and show a surprising marked trend with temperature, which further supports our suspicion of the presence of non-LTE eﬀects. Moreover, similar trends with temperature suggest that the Li and K underabundances in cool M34 dwarfs are partially related; thus, some portion of the well-known Li-Teﬀ trend in cool M34 dwarfs may be illusory.
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