Detection of variable elliptical polarization of HD 129333

HD 129333 is a single, solar-type dwarf with a probable age of about 70 Myr. It is a rapid rotator (about 2.7 d) with a high level of magnetic activity, consistent with its extreme youth. This paper reports on the discovery that HD 129333 is a polarimetric variable. Broadband observations on 17 nights in 1989 show that it has an approximately constant net linear polarization at the level of 0.1 percent, but there is a smooth variation in the position angle with an apparent period of about 14 days. There is also a variable net circular polarization of about 1 percent, but there is insufficient data to reveal a periodicity, if any. The net circular polarization is probably of magnetic origin, but there is not immediate explanation of the net linear polarization and its possible 14 day variation. A magnetic origin would appear to be excluded. Scattering in circumstellar material appears to be a more likely candidate, though it is difficult to explain the 14 day period if it is a single star. The possibility that HD 129333 is actually a binary with this period cannot be ruled out. 21 refs