A Multiwavelength View of ρ Oph. II. Disentangling the Variability of the Multistar Component C

We present a multiwavelength analysis of the star ρ Oph C, covering X-ray, optical, near-infrared (NIR), and radio observations to test for the presence of interferometrically detected cool star companions. The X-ray observations from Chandra, XMM-Newton, and NuSTAR show flare-like events lasting minutes or days in time and have spectral properties consistent with those of cooler stars instead of the primary magnetic B star. The NIR data are also consistent with the proposed trinary system properties due to the presence of CO bandheads. After removing the primary B star’s rotation, the optical data from TESS show a residual signal at the level of 0.8 mmag, matching the variations expected from cool stars in orbit around a bright B star. Finally, multiepoch radio data reveal that ρ Oph C exhibits significant large-scale flux variations that are atypical for a magnetic massive star. Taken as a whole, the multiepoch and -wavelength data present a consistent picture of ρ Oph C as a rare trinary system composed of a hot star and two cool stars.