Two optically dull galaxies with strong nuclear X-ray sources.

The paper reports the detection by the Einstein Observatory High Resolution Imager of compact, probably variable, X-ray sources in the nuclei of NGC 3862 (= 3C 264) and NGC 4156 with luminosities of the order of 10 to the 42nd ergs/s (0.5-4.5 keV). Neither galaxy has an optical spectrum that would suggest such strong activity. One of the galaxies, NGC 4156, has the weakest emission line fluxes of any known X-ray active galaxy. Its H-beta/L-x ratio, however, is in keeping with previous results. The other galaxy, NGC 3862, has a normal galactic absorption line spectrum with no detectable Balmer emission, putting its H-beta/L-x ratio clearly above the expected value; this suggests its nucleus is similar to a low-luminosity BL Lac object.