X-ray emission from A-type stars

Being fully radiative, stars of spectral type A are not expected to harbour magnetic dynamos and hence such stars are not expected to produce X-ray emission. Indeed, while the X-ray detection rate of such stars in X-ray surveys is low, it is not zero and some of the brighter A-type stars have been detected on different occasions and with different instruments. In order to systematically study the puzzle of the X-ray emitting A-type stars, we carried out an X-ray study of all A-type stars listed in the Bright Star Catalogue using the ROSAT public data archive. We found a total of 300 bright A-type stars positionally associated with ROSAT X-ray sources; we analysed the X-ray light curves as well as searched for evidence of RV variations to identify possible late-type companions producing the X-ray emission. We present a list of "bona fide" A-type stars, which axe secure X-ray sources without any evidence (so far) of unresolved companions.