Radio Detection of 18 RASS BL Lac Objects

We present the radio detection of 18 BL Lac objects from our survey of over 575 deg^2 of sky. These 18 objects are located within 20 arcsec of the X-ray position, 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, α_{RO} vs α_{OX}, 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(ν_{peak})≈ 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.