Context : The onset of stellar magnetic activity is related to the operation of dynamo processes that require the development of an outer convective layer .
This transition of stellar interior structure is expected to occur in late A-type stars .

Aims : The A7 star Altair is one of the hottest magnetically active stars .
Its proximity to the Sun allows a detailed investigation of a corona in X-rays for a star with a shallow convection zone .

Methods : We used a deep XMM-Newton observation of Altair and analyzed X-ray light curves , spectra , and emission lines .
We investigated the temporal behavior and properties of the X-ray emitting plasma and studied the global coronal structure of Altair .

Results : Altair ’ s corona with an X-ray luminosity of L _ { X } = 1.4 \times 10 ^ { 27 } erg/s and an activity level of \log L _ { X } / L _ { bol } = -7.4 is located predominantly at low latitude regions and exhibits X-ray properties that are overall very similar to those of other weakly active stars .
The X-ray emission is dominated by cool plasma ( 1 – 4 MK ) at low density , and elemental abundances exhibit a solar-like FIP effect and Ne/O ratio .
The X-ray brightness varies by 30 % over the observation , most likely due to rotational modulation and minor activity ; in contrast , no strong flares or significant amounts of hot plasma were detected .
The X-ray activity level of Altair is apparently close to the saturation level , which is reduced by roughly four orders of magnitude when compared to late-type stars .

Conclusions : With its fast rotation , Altair provides an inefficient , but very stable dynamo that mainly operates in convective layers below its ‘ cooler ’ surface areas around the equator .
This dynamo mechanism results in magnetic activity and leads to X-ray properties that are similar to those of the quiescent Sun , despite very different underlying stars .