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Astron. Astrophys. 328, L17-L20 (1997)

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3. Another BL LAC associated with a bright seyfert

The BL Lac object paired across NGC4235 adds to the list of 4 BL Lac's near Seyferts (Arp 1997a). BL Lac's are rare: they comprise only 4% of the X-ray sources in the Einstein Medium Sensitivity Survey (Stocke et al.1991). Even though the percentage increases appreciably for bright X-ray sources, the present case strengthens the previously found associations.

But this is only the sample so far investigated. There are obvious further candidates for BL Lac's around NGC1068, NGC7314 and NGC2992 and perhaps others as well. Moreover there are associated, strong X-ray, strong radio AGN's like the Sey 1 near NGC3516 and some of the stronger X-ray quasar which are closely allied to BL Lac's. As a particularly bright and easily identifiable kind of quasar, BL Lac's are particularly conspicuous objects with which to test the association with low redshift, bright Seyferts.

Two further comments are: 1) The BL Lac association is not a new result in the sense that it was reported 18 years ago that excess numbers of BL Lac's were found at a mean radial separation of about one deg. around bright apparent magnitude, Shapley-Ames galaxies (Sulentic et al. 1979). 2) To see a very flat logN/logS distribution for BL Lac's would imply that they were quite nearby in spite of their moderately large redshifts (see Arp 1990).

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© European Southern Observatory (ESO) 1997

Online publication: March 26, 1998