Context : Accurate atomic data is an essential ingredient for the calculation of reliable non-local thermodynamic equilibrium ( NLTE ) model atmospheres that are mandatory for the spectral analysis of hot stars .

Aims : We aim to search for and identify for the first time spectral lines of copper ( atomic number Z = 29 ) and indium ( Z = 49 ) in hot white dwarf ( WD ) stars and to subsequently determine their photospheric abundances .

Methods : Oscillator strengths of Cu iv - vii were calculated to include radiative and collisional bound-bound transitions of Cu in our NLTE model-atmosphere calculations .
Oscillator strengths of In iv - vi were compiled from the literature .

Results : We newly identified 1 Cu iv , 51 Cu v , 2 Cu vi , and 5 In v lines in the ultraviolet ( UV ) spectrum of DO-type WD RE 0503 $ - $ 289 .
We determined the photospheric abundances of 9.3 \times 10 ^ { -5 } ( mass fraction , 132 times solar ) and 3.0 \times 10 ^ { -5 } ( 56 600 times solar ) , respectively ; we also found Cu overabundances in the DA-type WD G191 $ - $ B2B ( 6.3 \times 10 ^ { -6 } , 9 times solar ) .

Conclusions : All identified Cu iv-vi lines in the UV spectrum of RE 0503 $ - $ 289 were simultaneously well reproduced with our newly calculated oscillator strengths .
With the detection of Cu and In in RE 0503 $ - $ 289 , the total number of trans-iron elements ( Z > 28 ) in this extraordinary WD reaches an unprecedented number of 18 .