DOI: 10.2298/SAJ0979007A Original scientific paper RADIO DETECTION OF 18 RASS BL LAC OBJECTS

SUMMARY: We present the radio detection of 18 BL Lac objects from our sur-vey of over 575 deg2 of sky. These 18 objects are located within 20′ ′ of the X-ray posi-tion, of which 11 have a measured red-shift. All candidates are radio emitters above ∼1 mJy and fall within the range of existing samples on the two colour, αRO vs αOX, diagram with a transitional population of three evident. Two unusual sources have been identified, a candidate radio quiet BL Lac, RX J0140.9–4130, and an extreme HBL, RX J0109.9–4020, with log (νpeak) ≈ 19.2. The BL Lac log(N) − log(S) relation is consistent with other samples and indicates the ROSAT All Sky Survey (RASS) could contain (2000±400) BL Lac objects. Key words. Galaxies: active — BL Lacertae objects: general — quasars: general 1