Context : The CoRoT mission is in its third year of observation and the data from the second long run in the galactic centre direction are being analysed .
The solar-like oscillating stars that have been observed up to now have given some interesting results , specially concerning the amplitudes that are lower than predicted .
We present here the results from the analysis of the star HD 170987 .

Aims : The goal of this research work is to characterise the global parameters of HD 170987 .
We look for global seismic parameters such as the mean large separation , maximum amplitude of the modes , and surface rotation because the signal-to-noise ratio in the observations do not allow us to measure individual modes .
We also want to retrieve the stellar parameters of the star and its chemical composition .

Methods : We have studied the chemical composition of the star using ground-based observations performed with the NARVAL spectrograph .
We have used several methods to calculate the global parameters from the acoustic oscillations based on CoRoT data .
The light curve of the star has been interpolated using inpainting algorithms to reduce the effect of data gaps .

Results : We find power excess related to p modes in the range [ 400 - 1200 ] \mu Hz with a mean large separation of 55.2 \pm 0.8 \mu Hz with a probability above 95 % that increases to 55.9 \pm 0.2 \mu Hz in a higher frequency range [ 500 - 1250 ] \mu Hz and a rejection level of 1 \% .
A hint of the variation of this quantity with frequency is also found .
The rotation period of the star is estimated to be around 4.3 days with an inclination axis of i = 50 \degr ^ { +20 } _ { -13 } .
We measure a bolometric amplitude per radial mode in a range [ 2.4 - 2.9 ] ppm around 1000 \mu Hz .
Finally , using a grid of models , we estimate the stellar mass , M = 1.43 \pm 0.05 M _ { \odot } , the radius , R = 1.96 \pm 0.046 R _ { \odot } , and the age \sim 2.4 Gyr .

Conclusions :