Context : To understand the origin of stellar activity in pre-main sequence Herbig Ae/Be stars and to get a deeper insight in the interior of these enigmatic stars , the pulsational instability strip of Palla and Marconi is investigated .
In this article we present a first discovery of non radial pulsations in the Herbig Ae spectroscopic binary star RS Cha .

Aims : The goal of the present work is to detect for the first time directly by spectrographic means non-radial pulsations in a Herbig Ae star and to identify the largest amplitude pulsation modes .

Methods : The spectroscopic binary Herbig Ae star RS Cha was monitored in quasi-continuous observations during 14 observing nights ( Jan 2006 ) at the 1m Mt John ( New Zealand ) telescope with the Hercules high-resolution echelle spectrograph .
The cumulated exposure time on the star was 44 hrs , corresponding to 255 individual high-resolution echelle spectra with R = 45000 .
Least square deconvolved spectra ( LSD ) were obtained for each spectrum representing the effective photospheric absorption profile modified by pulsations .
Difference spectra were calculated by subtracting rotationally broadened artificial profiles ; these residual spectra were analysed and non-radial pulsations were detected .
A subsequent analysis with two complementary methods , namely Fourier Parameter Fit ( FPF ) and Fourier 2D ( F2D ) has been performed and first constraints on the pulsation modes have been derived .

Results : For the very first time we discovered by direct observational means using high resolution echelle spectroscopy non radial oscillations in a Herbig Ae star .
In fact , both components of the spectroscopic binary are Herbig Ae stars and both show NRPs .
The FPF method identified 2 modes for the primary component with ( degree \ell , azimuthal order m ) couples ordered by decreasing probability : f _ { 1 } = 21.11 d ^ { -1 } with ( \ell , m ) = ( 11,11 ) , ( 11,9 ) or ( 10,6 ) and f _ { 2 } = 30.38 d ^ { -1 } with ( \ell , m ) = ( 10,6 ) or ( 9,5 ) .
The F2D analysis indicates for f _ { 1 } a degree \ell = 8-10 .
For the secondary component , the FPF method identified 3 modes with ( \ell , m ) ordered by decreasing probability : f _ { 1 } = 12.81 d ^ { -1 } with ( \ell , m ) = ( 2,1 ) or ( 2,2 ) , f _ { \mathrm { 2 } b } = 19.11 d ^ { -1 } with ( \ell , m ) = ( 13,5 ) or ( 10,5 ) and f _ { 3 } = 24.56 d ^ { -1 } with ( \ell , m ) = ( 6,3 ) or ( 6,5 ) .
The F2D analysis indicates for f _ { 1 } a degree \ell = 2 or 3 , but proposes a contradictory identification of f _ { 2 } as a radial pulsation ( \ell = 0 ) .

Conclusions :