V733 Cep (Persson's Star): A New FU Orionis Object in Cepheus

Persson recently found that a faint star had appeared in a cloud in Cepheus. A CCD image shows a R ~ 17.3 nebulous star, now known as V733 Cep, located in the L1216 = Cep F cloud at the apex of a cavity in the cloud. Infrared photometry indicates a modest infrared excess. Optical spectroscopy shows a well-defined Li I l6707 line, and blueshifted absorption troughs at the Ha and Na I D lines extending to at least 200 km s-1, indicative of a massive fast wind. An infrared 1-4 mm spectrum of V733 Cep shows the presence of strong water vapor features, and is almost identical to a similar IR spectrum of FU Ori that is reddened by AV = 8 mag. Assuming an intrinsic energy distribution similar to that of FU Ori, V733 Cep has a luminosity of about 135 L at the assumed distance of 800 pc. The star was detected by the Midcourse Space Experiment satellite at 8.3 mm, but not by IRAS. Nor is it detected at 850 mm, indicating that while the star possesses circumstellar material it is not surrounded by a significant cool envelope. A 12CO(3-2) map shows what appears to be a small molecular outflow along the same axis as the cavity seen in optical images. There is evidence for a limited amount of other low- and medium-mass star formation in the Cep F cloud. The totality of the evidence strongly indicates that V733 Cep is a new FU Ori-type object that must have erupted sometime between 1953 and 1984.