When high-dispersion analyses are performed, it is necessary to assume (often tacitly) that no corrections are required for some possible sources of systematic error for which inadequate information is available. In some papers, potential error sources of this kind are discussed explicitly (see Norris et al. 2001 and especially Carretta & Gratton 1997). That procedure also seems appropriate for the cataloging described here, and it was in fact adopted by T94. The review of uncorrected systematic effects given in that paper will be updated here.
In T94, there is a brief discussion of possible effects of chromospheric activity. Since that discussion was published, an extensive analysis of this problem has been produced by Valenti (1994). Judging from Valenti's work, there is good reason to suspect that chromospheric activity can affect some of the numerical results of high-dispersion analysis. However, if one asks about derived values of [Fe/H] in particular, the situation remains unclear. It is for this reason that possible chromospheric effects have not been considered above.
The widespread use of plane-parallel model atmospheres which are horizontally homogeneous is a possible problem which was not considered in T94. Here, a paper by Allende Prieto et al. (2001) is consulted for guidance. Those authors find that if a particular model atmosphere with structure like that described above is used, derived solar abundances are within 10% of the correct abundances. Admittedly it would be premature to generalize this result to all dwarfs and all model atmospheres that have been used to analyze them. However, it does seem fair to regard the work of Allende Prieto et al. as a reason for setting aside the issue at present.
A third possible problem is from nLTE effects, which have arguably attracted more concern than any other systematic effect considered in high-dispersion analysis. In this case, contradictory theoretical results have been published. On the one hand, Thévenin & Idiart (1999) find that nLTE effects on derived values of [Fe/H] can be appreciable for metal-poor dwarfs, but not for metal-rich dwarfs. On the other hand, Gratton et al. (1999) find that nLTE effects are not important for either metal-poor or metal-rich dwarfs. Norris et al. (2001) cite these studies as part of their reason for omitting nLTE effects from their analysis. The same reasoning is applied here.
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