Two New Bl-Lacertae Objects Discovered in the Error Boxes of Hard X-Ray Sources
Tagliaferri, G.; Beuermann, K.; Branduardi-Raymont, G.; Giommi, P.; Mason, K. O.; Brissenden, R.; Murdin, P.; Thomas, H. -C.; Tuohy, I.
Netherlands, Germany, United Kingdom, Australia
Abstract
Two new BL Lacertae objects, located within the error boxes of hard X-ray sources, have been discovered during a systematic program to identify a large sample of EXOSAT serendipitous sources. Both hard X-ray sources were detected during the HEAD 1 whole sky survey and have been associated to a Seyfert galaxy and to a Be star. The EXOSAT data are consistent with the two BL Lacs being the only counterparts of the hard X-ray sources. If this is the case the space density of BL Lacs, at fluxes 3 x 10-11 erg cm -2 s -1 (2-10 keV), might be higher than previously thought. The implications for the shape on the X-ray LogN-LogS of BL Lac objects are briefly discussed.