Oxygen abundance of open cluster dwarfs

Abstract

We present oxygen abundances of dwarfs in the young open cluster IC 4665 deduced from the OI $\lambda$7774 triplet lines and of dwarfs in the open cluster Pleiades derived from the [OI] $\lambda$6300 forbidden line. Stellar parameters and oxygen abundances were derived using the spectroscopic synthesis tool SME (Spectroscopy Made Easy). We find a dramatic increase in the upper boundary of the OI triplet abundances with decreasing temperature in the dwarfs of IC 4665, consistent with the trend found by Schuler et al. in the open clusters Pleiades and M 34, and to a less extent in the cool dwarfs of Hyades (Schuler et al. 2006a) and UMa (King & Schuler 2005). By contrast, oxygen abundances derived from the [OI] $\lambda$6300 forbidden line for stars in Pleiades and Hyades (Schuler et al. 2006b) are constant within the errors. Possible mechanisms that may lead a varying oxygen triplet line abundance are examined, including systematic errors in the stellar parameter determinations, the NLTE effects, surface activities and granulation. The age-related effects stellar surface activities (especially the chromospheric activities) are suggested by our analysis to blame for the large spreads of oxygen triplet line abundances.

11 pages, 5 figures. ApJ in press

References in corpus (5)

• Astrophysical parameters of Galactic open clusters
• The Evolution of the Water Distribution in a Viscous Protoplanetary Disk
• Oxygen from the Lambda 7774 High-Excitation Triplet in Open Cluster Dwarfs: Hyades
• High-Resolution Spectroscopy of Ursa Major Moving Group Stars
• Spectroscopic abundance analysis of dwarfs in young open cluster IC 4665

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• Does the solar oxygen abundance change over the solar cycle? An investigation into activity-induced variations of the O I infrared triplet