Optical Observations of the Radio Source 0735+178

Abstract

It is shown that the variable radio source 0735+178, which has no optical emission lines in its spectrum, varies substantially in both optical flux (AinB 1 mag) and polarization (5-30 percent) on time scales less than a month. It is therefore assigned to the class of objects containing BL Lac and OJ 287. The spectrum of 0735+178 does, however, contain two sharp absorption features at 3981 and 3991 A which are identified with the Mg ii X2798 doublet at a red- shift z = 0.424. This confirms that 0735+178 is extragalactic with similar implications for other members of the class. The presence of highly redshifted absorption lines in 0735+178 also strengthens the hypothesis that these objects are similar to quasars. Subject headings: quasi-stellar sources or objects - radio sources, variable - redshifts