B-TYPE EMISSION LINE STARS
In collaboration with D. Gies, Georgia State University, Peters is continuing an investigation of Be-type interacting binaries whose secondaries might be O-type subdwarfs. These hot subdwarfs are the stripped-down remnants of stars that were originally more massive than the present primary star. Presumably the mass transfer process added angular momentum to the mass gainer (typically a very rapid rotator of ∼0.8 Vcrit ) which then became a Be star (it is believed that rapid rotation is important in producing the Be phenomenon). We confirmed from HST and IUE data that one long-period (126d) system, φ Per, indeed has an O subdwarf companion (Gies et al. 1998, ApJ, 493, 440). Later we combined spectra of the Be star FY CMa taken with the IUE spacecraft and KPNO Coudé Feed Telescope over the course of 15-20 years to confirm that this star is also a binary system with an O subdwarf companion (Peters, et al. 2008, ApJ, 686, 1280). In a similar study we further confirmed that the well-known bright Be star 59 Cyg also harbors an sd-O secondary (Peters, et al. 2013, ApJ, 765, A2).