3A 0729+103

I. M. McHardy and J. P. Pye, University of Leicester; A. P. Fairall, B. Warner, S. Allen and M. Cropper, University of Cape Town; and M. J. Ward, Institute of Astronomy, Cambridge, report the identification of the x-ray source 3A 0729+103 with a newly discovered catac1ysmic variable of mag ~14.5, based on an arcmin-precision position obtained from an Einstein IPC guest observation. Extensive photometry in white light with 10-s time resolution shows stochastic flickering and occasional flares (of amplitude 5 percent) superimposed on a coherent sinusoidal pulsation of period 913s.48 and mean amplitude 12 percent. There may be an orbital modulation of period 3.75 hr and amplitude 8 percent. The x-ray observations also show evidence of a period of ~ 900-1000s. Low resolution optical spectra show broad He and Balmer lines, up to H11, in emission. The lines have fwzi of ~ 1600 km/s and vary in strength through the 913-s period, with most variation being noticed in the higher Balmer lines. High-resolution optical spectra show that many emission lines have multiple components. The star is at R.A. = 7h28m44s.4, Decl. = +10o02'46" (+/- 1".5, equinox 1950.0).