EXO 023432-5232.3

K. Beuermann, Technische Universitat Berlin and MPI fur Extraterrestrische Physik, Garching; H.-C. Thomas, MPI fur Astrophysik, Garching; and P. Giommi and G. Tagliaferri, EXOSAT Observatory, Space Science Dept. of ESA, report the discovery of a new x-ray emitting probable AM Her binary. The source, located at 2h34m31s.8, -52 32'19" (equinox 1950.0, uncertainty +/-7"), was found as a serendipitous x-ray source with the low energy telescope of the EXOSAT satellite. The mean count rate was 8.6 x 10-3 cts/s, obtained with the CMA detector and the 3000 Lexan filter. The position permitted unique identification with a 19-mag star. CCD spectrophotometry obtained in 1986 July and Oct. using the MPI 2.2-m telescope at ESO revealed a high-excitation emission-line spectrum with a He II 469 nm:H beta intensity ratio of 0.35, a spectroscopic and photometric orbital period of 114.62 +/- 0.02 min, and a K-value of 388 +/- 20 km/s, obtained from a single-gaussian fit to the Balmer lines. The orbital lightcurve is similar to that of the AM Her stars 1E 1048.5+5421 and E1114+182, with a pronounced dip occurring at radial velocity maximum. Orbital light variation outside the dip is mainly due to a red continuum. Although polarimetry is still lacking, EXO 023432-5232.3 is almost certainly an AM Her star, the sixth AM Her star found in the period interval 113-115 min. Polarimetry of the system is encouraged.