The 17 O(p, α) 14 N and 17 O(p, γ ) 18 F reactions are of major importance to hydrogen-burning nucleosynthesis in a number of different stellar sites. In particular, 17 O and 18 F nucleosynthesis in classical novae is strongly dependent on the thermonuclear rates of these two reactions. The previously estimated rate for 17 O(p, α) 14 N carries very large uncertainties in the temperature range of classical novae (T = 0.01-0.4 GK), whereas a recent measurement has reduced the uncertainty of the 17 O(p, γ ) 18 F rate. We report on the observation of a previously undiscovered resonance at E c.m. = 183.3 keV in the 17 O(p, α) 14 N reaction, with a measured resonance strength ωγ pα = (1.6 ± 0.2) × 10 −3 eV. We studied in the same experiment the 17 O(p, γ ) 18 F reaction by an activation method, and the resonance strength was found to amount to ωγ pγ = (2.2 ± 0.4) × 10 −6 eV. The excitation energy of the corresponding level in 18 F was determined to be 5789.8 ± 0.3 keV in a Doppler shift attenuation method measurement, which yielded a value of τ < 2.6 fs for the level lifetime. The 17 O(p, α) 14 N and 17 O(p, γ ) 18 F reaction rates were calculated using the measured resonance properties and reconsidering some previous analyses of the contributions of other levels or processes. The 17 O(p, α) 14 N rate is now well established below T = 1.5 GK, with uncertainties reduced by orders of magnitude in the temperature range T = 0.1-0.4 GK. The uncertainty in the 17 O(p, γ ) 18 F rate is somewhat larger because of remaining obscurities in the knowledge of the direct capture process. These new resonance properties have important consequences for 17 O nucleosynthesis and γ -ray emission of classical novae.A. CHAFA et al. PHYSICAL REVIEW C 75, 035810 (2007) 035810-2 E R (keV) a