DISCOVERY OF A NEW BL LACERTAE OBJECT (1E1402.3 + 0416) WITH THE EINSTEIN-OBSERVATORY

One (and only one) BLLac object, designated IE 1402.3 + 0416, has been so far discovered as part of an optical identification program for a complete sample of faint X-ray sources detected with the Einstein Observatory. Consistent with earlier X-ray discovered BLLacs, this object is blue (aopt - — 1) and radio weak (17mJy at 6 cm). The percentage of BLLacs in the faint extragalactic X-ray sample (2 per cent) is smaller than the percentage at higher X-ray fluxes (6 per cent). Over the same range in X-ray flux, the percentage of emission-line active galaxy nuclei (QSO + Seyferts) increases from 40 to 74 per cent. This suggests that BLLacs do not evolve in a manner similar to quasars (> 4a confidence level) and are, therefore, not substantial contributors (^ 5 per cent) to the X-ray background. © Royal Astronomical Society.