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We present new abundances derived from Cu I, Cu II, Zn I, and Zn II lines insix warm (5766 < Teff < 6427 K), metal-poor (-2.50 < [Fe/H] < -0.95) dwarf andsubgiant (3.64 < log g < 4.44) stars. These abundances are derived fromarchival high-resolution ultraviolet spectra from the Space Telescope ImagingSpectrograph on board the Hubble Space Telescope and ground-based opticalspectra from several observatories. Ionized Cu and Zn are the majority species,and abundances derived from Cu II and Zn II lines should be largely insensitiveto departures from local thermodynamic equilibrium (LTE). We find goodagreement between the [Zn/H] ratios derived separately from Zn I and Zn IIlines, suggesting that departures from LTE are, at most, minimal (< 0.1 dex).We find that the [Cu/H] ratios derived from Cu II lines are 0.36 +/- 0.06 dexlarger than those derived from Cu I lines in the most metal-poor stars ([Fe/H]< -1.8), suggesting that LTE underestimates the Cu abundance derived from Cu Ilines. The deviations decrease in more metal-rich stars. Our results validateprevious theoretical non-LTE calculations for both Cu and Zn, supportingearlier conclusions that the enhancement of [Zn/Fe] in metal-poor stars islegitimate, and the deficiency of [Cu/Fe] in metal-poor stars may not be aslarge as previously thought.

A New Test of Copper and Zinc Abundances in Late-Type Stars Using Ultraviolet Cu II and Zn II Lines