Measurement of B→Xγ Decays and Determination of |V_{td}/V_{ts}|

Using a sample of 383 x 10;{6} BB[over ] events collected by the BABAR experiment, we measure sums of seven exclusive final states B-->X_{d(s)}gamma, where X_{d}(X_{s}) is a nonstrange (strange) charmless hadronic system in the mass range 0.6-1.8 GeV/c;{2}. After correcting for unmeasured decay modes in this mass range, we obtain a branching fraction for b-->dgamma of (7.2+/-2.7(stat)+/-2.3(syst))x10;{-6}. Taking the ratio of X_{d} to X_{s} we find Gamma(b-->dgamma)/Gamma(b-->sgamma)=0.033+/-0.013(stat)+/-0.009(syst), from which we determine |V_{td}/V_{ts}|=0.177+/-0.043.