The pre-main-sequence binary HK Ori: Spectro-astrometry and EXPORT data
Baines D., Oudmaijer RD., Mora A., Eiroa C., Porter JM., Merín B., Montesinos B., De Winter D., Cameron A., Davies JK., Deeg HJ., Ferlet R., Grady CA., Harris AW., Hoare MG., Horne K., Lumsden SL., Miranda LF., Penny A., Quirrenbach A.
In this paper we present multi-epoch observations of the pre-main-sequence binary HK Ori. These data have been drawn from the EXPORT data base and are complemented by high-quality spectro-astrometric data of the system. The spectroscopic data appear to be very well represented by a combination of an A dwarf star spectrum superposed on a (sub)giant G-type spectrum. The radial velocity of the system is consistent with previous determinations, and does not reveal binary motion, as expected for a wide binary. The spectral, photometric and polarimetric properties and variability of the system indicate that the active object in the system is a T Tauri star with UX Ori characteristics. The spectro-astrometry of HK Ori is sensitive down to milliarcsecond scales and confirms the speckle interferometric results from Leinert et al. The spectro-astrometry allows the identification, with fair certainty, of the active star within the binary, which we suggest to be a G-type T Tauri star based on its spectral characteristics.