2001ApJ...547..590G

We present a method to measure the ratio of total to selective extinction, R_VI≡A_V/E(V-I), toward Baade's window by comparing the VIK colors of 146 Baade's window G and K giants from Tiede, Frogel, & Terndrup with the solar neighborhood (V-I), (V-K) relation from Bessell & Brett. We show that the statistical errors of this approach are ∼0.7%, an order of magnitude smaller than the only previous measurement of this quantity, and that the measurement has at most a weak dependence on stellar type from G0 to K4. However, the systematic error, which arises from uncertainties in the photometric zero points, is much larger: using the Tiede et al. zero points we obtain R_VI=2.28, while the OGLE II zero points yield R_VI=2.40, a difference of 5%. Hence, determination of the photometric zero points will be critical to obtaining an unambiguous measurement of R_VI.