Context : The NASA Kepler space telescope has detected solar-like oscillations in several hundreds of single stars , thereby providing a way to determine precise stellar parameters using asteroseismology .

Aims : In this work , we aim to derive the fundamental parameters of a close triple star system , HD 188753 , for which asteroseismic and astrometric observations allow independent measurements of stellar masses .

Methods : We used six months of Kepler photometry available for HD 188753 to detect the oscillation envelopes of the two brightest stars .
For each star , we extracted the individual mode frequencies by fitting the power spectrum using a maximum likelihood estimation approach .
We then derived initial guesses of the stellar masses and ages based on two seismic parameters and on a characteristic frequency ratio , and modelled the two components independently with the stellar evolution code CESTAM .
In addition , we derived the masses of the three stars by applying a Bayesian analysis to the position and radial-velocity measurements of the system .

Results : Based on stellar modelling , the mean common age of the system is 10.8 \pm 0.2 { Gyr } and the masses of the two seismic components are M _ { A } = 0.99 \pm 0.01 M _ { \odot } and M _ { Ba } = 0.86 \pm 0.01 M _ { \odot } .
From the mass ratio of the close pair , M _ { Bb } / M _ { Ba } = 0.767 \pm 0.006 , the mass of the faintest star is M _ { Bb } = 0.66 \pm 0.01 M _ { \odot } and the total seismic mass of the system is then M _ { syst } = 2.51 \pm 0.02 M _ { \odot } .
This value agrees perfectly with the total mass derived from our orbital analysis , M _ { syst } = 2.51 ^ { +0.20 } _ { -0.18 } M _ { \odot } , and leads to the best current estimate of the parallax for the system , \pi = 21.9 \pm 0.2 { mas } .
In addition , the minimal relative inclination between the inner and outer orbits is 10.9 ^ { \circ } \pm 1.5 ^ { \circ } , implying that the system does not have a coplanar configuration .

Conclusions :