Appendix A: Sample information

Table 3 gives information about the ROSAT observation.

Column 1: the ROSAT name of the object, composed of the prefix RXJ and a short form of the coordinates.

Column 2: the coordinates of the X-ray source, as determined from the ROSAT plates (equinox 2000.0). The error for these positions is typically 30$^{\prime\prime}$.

Column 3: the countrates for the X-ray sources, in counts per second.

Column 4: the total exposure time for each source.

Column 5: the hardness ratio 1 of each source.

Column 6: the coordinates, also for equinox 2000.0, of the stellar counterparts of the ROSAT sources.

Column 7: the distance between the X-ray position, as listed in Table 3 and the position of the counterpart, in arcseconds.

Column 8: the results from the spectral classification for the sample stars. For the binaries, the fact that the binarity/multiplicity obtained from the photometry was confirmed by the high-resolution spectra is indicated by a subscripted 1. A subscript 2 means the binarity was determined from the high-resolution spectra, a 3 means the binary is a visual one and a 4 means the binarity information was only obtained through the literature.

Column 9: the distance of the stars from the Sun, in pc, as determined using their (B-V) colour index (see Sect. 2.4).

Column 10: the X-ray flux of the X-ray sources, in units of $10^{-12} \ {\rm erg} \ {\rm s}^{-1} \ {\rm cm}^{-2}$, as well as the errors for the flux.

Column 11: the X-ray luminosities of the studied stars, in units of $10^{29} \ {\rm erg} \ {\rm s}^{-1}$,as well as the errors, as determined using the errors of the distance and X-ray flux.

Column 12: a catalogue name, whenever exiting.

Column 13: the spectral classification obtained either from the SIMBAD database or the low-resolution spectra taken in the course of the identification program.

Columns 14-17: the apparent visual magnitude and colours, in the $BV(RI)_{\rm C}$ of the counterpart.