Motivated by the existence of binary systems where a stellar-mass black hole is bound to a normal star , we selected four red giants with large radial velocity ( RV ) variation from the survey of Space Interferometry Mission ( SIM ) grid stars and monitored their RVs for several months .
None turned out to contain a massive companion above 2.5 solar masses .
The red giant TYC 9299-1080-1 with a large RV and a large proper motion is a single-lined spectroscopic binary with a period of 81 days .
It is an extreme halo object moving at 350 km s ^ { -1 } almost directly toward the Galactic center .
HD 206092 is a double-lined binary with a short period of 4.37 days .
It belongs to the rare class of active RS CVn-type binaries with evolved primary components , apparently undergoing mass transfer .
The X-ray luminosity of HD 206092 is about twice as high as the most luminous coronal X-ray emitters observed by ROSAT , including II Peg and the prototype star RS CVn .
HD 318347 has a variable double-peaked emission-line spectrum ( not a giant ) , while HD 324668 has a constant RV .
Despite the overall good quality of the SIM survey data confirmed by a comparison with Gaia Data Release 2 ( DR2 ) mean radial velocities , the few large RV variations are explained , mostly , by erroneous data .
We discuss the significance of the non-detection of massive companions in the SIM grid sample and the associated work .