Zeta$^2$ Coronae Borealis, A Spectroscopic Triple System Including an Asynchronous Close Binary

Gordon, K. D., & Mulliss, C. L.
1997, Publications of the Astronomical Society of the Pacific, 109, 221

Using the 1-m telescope at Ritter Observatory, we took 36 observations of \zeta$^2$ Coronae Borealis with a fiber-fed echelle spectrograph. From these observations, \zeta$^2$ CrB was found to be a triple system and a new spectroscopic orbit was calculated. This orbit has two periods, a 1.72357 day period for the inner binary composed of \zeta$^2$ CrB A $&$ B and a 251 day period for the outer binary compsed of \zeta$^2$ CrB AB $&$ C. The inner binary is a double-lined spectroscopic binary composed of two B7 V stars. The inner binary`s center of mass (\zeta$^2$ CrB AB) describes a long-period single-lined variation identified with the outer binary. The inner binary period is significantly shorter than the 12.5842 day period previously calculated by Abhyankar $&$ Sarma (1966). The inner binary possesses an essentially circular orbit $(e = 0.48)$. From the widths of their Si II 6371 \AA lines, the \upsilon sin $i$'s were calculated to be 46 \pm 7 km s$^-1$ for \zeta$^2$ CrB A and 7.5 \pm 2 km s$^-1$ for \zeta$^2$ CrB B. As \zeta$^2$ CrB A $&$ B have similar masses, their different rotational velocities make this system a sensitive test of synchronization theories. (SECTION: Stars)

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