X-ray emission from A0-F6 spectral type stars

We use the ROSAT public data archive to study the X-ray emission of a sample of supposedly single A0-F6 spectral type stars from the Bright Star Catalogue. We detected X-ray emission from 19 A- and 33 F-type stars. However, our results are not sufficient to associate with certainty the X-ray emission to the A-type stars themselves, since the usual argument that it may originate from a binary companion cannot be excluded. A spectral analysis was conducted for 14 sources (3 A and 11 F), finding that for 12 of them a two temperature thermal plasma model is needed to reproduce the observed spectra. The two tem- peratures are centered at 0.13 and 0.54 keV, respectively. The values found for the higher temperature are lower than that ones of X-ray selected single late-type stars. The X-ray luminosities are in the range LX 10 28 -10 30 erg s 1 , with a distribution similar to that of active late-type stars. No correlation is found between LX and B-V color, V sin i and Lbol, while a posi- tive correlation is found between the X-ray luminosity and the hardness ratio.