CONTRIBUTION TO THE STUDY OF F , G , K , M BINARIES

IX .
HD 191588 , A NEW RS CVN-TYPE SINGLE-LINED

SPECTROSCOPIC BINARY , A TRIPLE SYSTEM

Abstract : An accident of misidentification has brought to light the interesting system HD 191588 , a new RS CVn-type spectroscopic binary .
A radial-velocity study of the primary star , the only seen component , carried out at the Observatoire de Haute-Provence with the Coravel instrument and subsequently at the Cambridge Observatories with a similar one , reveals two orbital motions : a short-period orbit ( 60 days ) and a long-period one ( about 4.5 years ) , so this star is a triple system . The following orbital elements are obtained : ( 1 ) for the long-period orbit P = 1667 \pm 17 days , T = 50901 \pm 67 MJD , \Gamma = +2.09 \pm 0.07 km s ^ { -1 } , K = 2.51 \pm 0.13 km s ^ { -1 } , e = 0.18 \pm 0.04 , \omega = 228 ^ { \circ } \pm 14 ^ { \circ } , a _ { 1 } \sin i = 56.7 \pm 3.0 Gm , f ( m ) = 0.0026 \pm 0.0004 M _ { \odot } , and ( 2 ) for the short-period orbit P = 60.0269 \pm 0.0016 days , T = 50482.6 \pm 3.3 MJD , \gamma is var. , K = 24.03 \pm 0.09 km s ^ { -1 } , e = 0.012 \pm 0.004 , \omega = 233 ^ { \circ } \pm 19 ^ { \circ } , a _ { 1 } \sin i = 19.83 \pm 0.07 Gm , f ( m ) = 0.0865 \pm 0.0009 M _ { \odot } . From near-infrared observations we refine the classification of the primary component and we found a spectral type of K2.5 III , and a spectrum obtained in the blue–near-UV spectral region reveals strong H and K emission lines of Ca II .
The unseen secondary should be a solar-type star ( F or G V ) ; the minimum mass of the third body is that of a dwarf M star .
Probably , the primary component rotates in synchronism with the orbital motion in the inner orbit ; a model , based upon that hypothesis , is proposed for the system , and finally the connection of the inner binary to the long-period RS CVn group ( Hall 1976 ) is discussed .