ONSs candidates

To date, plausible evidence for ONS candidates has been presented by Stocke et al. (1995) and Walter, Wolk & Neuhauser (1996), who found that two unidentified X-ray sources detected in either the Einstein Extended Medium Sensitivity Survey or in the ROSAT All Sky Survey may actually be powered by an accreting ONS. Another candidate has been presented by Haberl et al. (1996).