Context : The distance to the Galactic Centre ( GC ) is of importance for the distance scale in the Universe .
The value derived by Eisenhauer et al .
( 2005 ) of 7.62 \pm 0.32 kpc based on the orbit of one star around the central black hole is shorter than most other distance estimates based on a variety of different methods .

Aims : To establish an independent distance to the GC with high accuracy .
To this end Population- ii Cepheids are used that have been discovered in the ogle - ii and ogle - iii surveys .

Methods : Thirty-nine Population- ii Cepheids have been monitored with the SOFI infrared camera on 4 nights spanning 14 days , obtaining typically between 5 and 11 epochs of data .
Light curves have been fitted using the known periods from the OGLE data to determine the mean K -band magnitude with an accuracy of 0.01-0.02 mag .
It so happens that 37 RR Lyrae stars are in the field-of-view of the observations and mean K -band magnitudes are derived for this sample as well .

Results : After correction for reddening , the period-luminosity relation of Population- ii Cepheids in the K -band is determined , and the derived slope of -2.24 \pm 0.14 is consistent with the value derived by Matsunaga et al .
( 2006 ) .
Fixing the slope to their more accurate value results in a zero point , and implies a distance modulus to the GC of 14.51 \pm 0.12 , with an additional systematic uncertainty of 0.07 mag .
Similarly , from the RR Lyrae K -band period-luminosity relation we derive a value of 14.48 \pm 0.17 ( random ) \pm 0.07 ( syst . ) .
The two independent determinations are averaged to find 14.50 \pm 0.10 ( random ) \pm 0.07 ( syst .
) , or 7.94 \pm 0.37 \pm 0.26 kpc .
The absolute magnitude scale of the adopted period-luminosity relations is tied to an LMC distance modulus of 18.50 \pm 0.07 .

Conclusions :