Cepheid distances from infrared long-baseline interferometry

Using our interferometric angular diameter measurements of seven classical Cepheids reported in Kervella et al. (2003, Paper I), complemented by previously existing measurements, we derive new calibrations of the Cepheids Period–Radius (P–R) and Period–Luminosity (P–L) relations. We obtain a P–R relation of logR = [0.767 ± 0.009] logP + [1.091 ± 0.011], only 1σ away from the relation obtained by Gieren et al. (1998). We therefore confirm their P–R relation at a level of ∆(logR) = ±0.02. We also derive an original calibration of the P–L relation, assuming the slopes derived by Gieren et al. (1998) from LMC Cepheids, αK = −3.267± 0.042 and αV = −2.769 ± 0.073. With a P–L relation of the form Mλ = αλ (logP − 1) + βλ, we obtain logP = 1 reference points of βK = −5.904 ± 0.063 and βV = −4.209 ± 0.075. Our calibration in the V band is statistically identical to the geometrical result of Lanoix et al. (1999).