Context : Blazars are radio-loud active galactic nuclei ( AGN ) with a jet pointing at small angles towards the observer .
The overall emitted spectrum is typically non-thermal , and in some cases the emission and/or absorption lines are so faint as to prevent the determination of the redshift based on optical spectroscopy methods .
PKS 0447 - 439 is a bright blazar recently detected at very high energy .
The redshift of the source is still disputed : a recent spectral analysis reports only a lower limit of z > 1.246 , which contradicts the previous measure of z = 0.205 reported in the literature .

Aims : We aim to give a redshift estimate of the blazar PKS 0447 - 439 based on combined GeV ( Fermi /LAT ) and TeV ( H.E.S.S . )
observations .

Methods : Taking into account the absorption of TeV photons by the interaction with the extragalactic background light ( EBL ) , we applied the method we developed in a previous work to derive the redshift of PKS 0447 - 439 .
Moreover , we compiled the overall spectral energy distribution ( SED ) using optical-UV , soft X–ray , and \gamma -ray data , nearly simultaneous to the H.E.S.S .
observations at TeV energies .
Finally we modelled the spectral energy distribution ( SED ) within the framework of a homogeneous , leptonic synchrotron self-Compton ( SSC ) model .

Results : Using the recent TeV spectrum measured by H.E.S.S .
we obtain for PKS 0447 - 439 a redshift of z _ { rec } = 0.20 \pm 0.05 , which is our estimate on the source distance .
This value agrees very well with the value reported in the literature and confirms that our method can be successfully used to constrain blazars distances .
Assuming this distance , the SED can be well fitted with the above mentioned model .
The physical parameters that we find suggest a strongly matter-dominated jet .

Conclusions : Our analysis confirms that the redshift of PKS 0447 - 439 is likely 0.2 , and supports the result present in the literature .