Radio-optical candidates for the high-latitude X-ray sources 3U 1555+27 and 3U 1809+50

Radio observations at 610 MHz with the Westerbork Synthesis Radio Telescope (WSRT) are combined with optical data from the 48 inch Palomar telescope to search for radio-optical candidates for five high-latitude Uhuru X-ray sources (3U 0042+32, 0917+63, 1443+43, 1555+27, and 1809+50). From the data for two of these fields we suggest the following: (1) The rich cluster of galaxies A2142 (zapprox. =0.1), which is found to contain several extended radio sources in its central region, is a likely candidate for 3U 1555+27, as first suggested from purely optical observations. (2) The ''near'' Zwicky cluster, Zw 1810.2+4949, which contains a complex radio source associated with a 15 mag galaxy, is a candidate identification for 3U 1809+50. The unusual radio galaxy OU 516, as well as the double galaxy NGC 6582, both located in the cluster, are also candidates for 3U 1809+50, especially if the X-rays indicate variability. (AIP)