2004A&A...416..941K

We report the angular diameter measurements of seven classical Cepheids, X Sgr, η Aql, W Sgr, ζ Gem, β Dor, Y Oph and l Car that we have obtained with the VINCI instrument, installed at ESO's VLT Interferometer (VLTI). We also present reprocessed archive data obtained with the FLUOR/IOTA instrument on ζGem, in order to improve the phase coverage of our observations. We obtain average limb darkened angular diameter values of <θ_LD>[XSgr]=1.471±0.033mas, <θ_LD>[ηAql]=1.839±0.028mas, <θ_LD>[WSgr]=1.312±0.029mas, <θ_LD>[βDor]=1.891±0.024mas, <θ_LD>[ζGem]=1.747±0.061mas, <θ_LD>[YOph]=1.437±0.040mas, and<θ_LD>[lCar]=2.988±0.012mas. For four of these stars, η Aql, W Sgr, β Dor, and l Car, we detect the pulsational variation of their angular diameter. This enables us to compute directly their distances, using a modified version of the Baade-Wesselink method: d[ηAql]=276⁺⁵⁵_–38pc, d[WSgr]=379⁺²¹⁶_–130pc, d[βDor]=345⁺¹⁷⁵_–80pc, d[lCar]=603⁺²⁴_–19pc. The stated error bars are statistical in nature. Applying a hybrid method, that makes use of the Gieren et al. (1998ApJ...496...17G) Period-Radius relation to estimate the linear diameters, we obtain the following distances (statistical and systematic error bars are mentioned): d[XSgr]=324±7±17pc, d[ηAql]=264±4 ±14pc, d[WSgr]=386±9 ±21pc, d[βDor]=326±4 ±19pc, d[ζGem]=360±13 ±22pc, d[YOph]=648±17±47pc, d[lCar]=542±2 ±49pc.