A Multiwavelength View of $\rho$ Oph II: Disentangling the Variability of the Multi-Star Component C

Abstract

We present a multiwavelength analysis of the star $\rho$ Oph C, covering X-ray, optical, near-infrared, 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 spectral properties consistent with those of cooler stars instead of the primary magnetic B star. The near-infrared data is also consistent with the proposed trinary system properties due to the presence of CO-band heads. After removing the primary B star's rotation, the optical data from TESS shows a residual signal at the level of 0.8 mmags, matching the variations expected from cool stars in orbit around a bright B star. Finally, multi-epoch radio data reveals that $\rho$ Oph C exhibits significant large scale flux variations that are atypical for a magnetic massive star. Taken as a whole, the multi-epoch and -wavelength data presents a consistent picture of $\rho$\,Oph\,C as a rare trinary system composed of a hot star and two cool stars.

27 pages, 8 figures, 6 tables, accepted for publication in ApJ, full list of contributing MACRO consortium members is provided in the Author Contribution section at the end of the manuscript