Rovibrational Spectroscopy of CI Tau—Evidence of a Multicomponent Eccentric Disk Induced by a Planet

Abstract

CI Tau is currently the only T Tauri star with an inner protoplanetary disk that hosts a planet, CI Tau b, that has been detected by a radial velocity survey. This provides the unique opportunity to study disk features that were imprinted by that planet. We present multiepoch spectroscopic data, taken with NASA IRTF in 2022, of the 12CO and hydrogen Pfβ line emissions spanning nine consecutive nights, which is the proposed orbital period of CI Tau b. We find that the star’s accretion rate varied according to that nine-day period, indicative of companion-driven accretion. Analysis of the 12CO emission lines reveals that the disk can be described with an inner and an outer component spanning orbital radii 0.05–0.13 au and 0.15–1.5 au, respectively. Both components have eccentricities of about 0.05 and arguments of periapsis that are oppositely aligned. We present a proof-of-concept hydrodynamic simulation that shows that a massive companion on a similarly eccentric orbit can recreate a similar disk structure. Our results allude to such a companion being located at an orbital distance of around 0.14 au. However, this planet’s orbital parameters may be inconsistent with those of CI Tau b, whose high eccentricity is likely not compatible with the low disk eccentricities inferred by our model.