Cepheid distances from infrared long-baseline interferometry - II. Calibration of the Period-Radius and Period-Luminosity relations

TL;DR

This study uses infrared long-baseline interferometry to refine the calibration of Cepheid Period-Radius and Period-Luminosity relations, confirming previous relations and providing new calibration constants for distance measurements.

Contribution

The paper presents new calibrations of Cepheid P-R and P-L relations based on interferometric data, confirming previous P-R relations and deriving original P-L calibration constants.

Findings

Confirmed P-R relation with high precision

Derived new P-L calibration constants in K and V bands

Validated calibration against previous geometrical results

Abstract

Using our interferometric observations 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 log R = [0.767 +/- 0.009] log P + [1.091 +/- 0.011], only 1 sigma away from the relation obtained by Gieren et al. (1998). We therefore confirm their P-R relation at a level of Delta(log R) = +/- 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, alpha_K = -3.267 +/- 0.042 and alpha_V = -2.769 +/- 0.073. With a P-L relation of the form M = alpha (log P - 1) + beta, we obtain log P = 1 reference points of beta(K) = -5.904 +/- 0.063 and beta(V) = -4.209 +/- 0.075. Our calibration in the V band is statistically identical to the geometrical result of Lanoix et al. (1999).