Context :

Aims : A strong decline of magnetic activity towards hotter stars occurs in the regime of mid/late A-type stars due to the vanishing of the outer convection zone .
X-ray emission is an important diagnostic of studying possible activity in intermediate-mass stars .

Methods : We present a Chandra observation of the exceptional planet bearing A5 V star HR 8799 , more precisely classified as a kA5 hF0 mA5 star and search for intrinsic X-ray emission .

Results : We clearly detect HR 8799 at soft X-ray energies with the ACIS-S detector in a 10 ks exposure ; minor X-ray brightness variability is present during the observation .
The coronal plasma is described well by a model with a temperature of around 3 MK and an X-ray luminosity of about L _ { X } = 1.3 \times 10 ^ { 28 } erg/s in the 0.2 – 2.0 keV band , corresponding to an activity level of log L _ { X } / L _ { bol } \approx - 6.2 .
Altogether , these findings point to a rather weakly active and given a RASS detection , long-term stable X-ray emitting star .

Conclusions : The X-ray emission from HR 8799 resembles those of a late A/early F-type stars , in agreement with its classification from hydrogen lines and effective temperature determination and thus resolving the apparent discrepancy with the standard picture of magnetic activity that predicts mid A-type stars to be virtually X-ray dark .