A Multiwavelength View of $\rho$ Oph I: Resolving the X-ray Source Between A and B

We present a multiwavelength analysis of the central stellar pair of $\rho$ Oph, components A and B. Using recent high-resolution $\mathit{\text{Chandra}}\mathit{\text{X-ray}}\mathit{\text{Observatory}}$ observations, we demonstrate with high confidence that the dominant X-ray source is $\rho$ Oph B, while $\rho$ Oph A is comparatively X-ray faint. This result contrasts with earlier $\mathit{\text{XMM-Newton}}$ observations, which, due to limited spatial resolutions, attributed the X-ray emission to $\rho$ Oph A. An analysis of $\rho$ Oph B’s X-ray light curves and spectra reveals properties more consistent with a cool star than a hot star. We therefore propose that $\rho$ Oph B is an Algol-like binary system, consisting of a B-type primary and an active, X-ray-emitting GK-type companion.