Ro-vibrational Spectroscopy of CI Tau -- Evidence of a Multi-Component Eccentric Disk Induced by a Planet

TL;DR

This study uses multi-epoch spectroscopy of CI Tau to reveal a multi-component eccentric disk likely shaped by a planet, providing insights into planet-disk interactions and potential planet properties.

Contribution

It presents the first detailed spectroscopic analysis of CI Tau's disk structure and proposes a hydrodynamic model demonstrating how a massive companion can induce observed features.

Findings

Disk has inner and outer components with eccentricities around 0.05.

Star's accretion rate varies with a 9-day period, indicating companion-driven accretion.

Hydrodynamic simulation supports a massive companion on an eccentric orbit shaping the disk.

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 multi-epoch spectroscopic data, taken with NASA IRTF in 2022, of the ${}^{12}$CO and hydrogen Pf$\beta$ line emissions spanning 9 consecutive nights, which is the proposed orbital period of CI Tau b. We find that the star's accretion rate varied according to that 9~d period, indicative of companion driven accretion. Analysis of the ${}^{12}$CO emission lines reveals that the disk can be described with an inner and 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 periapses that are oppositely aligned. We present a proof-of-concept hydrodynamic simulation that shows a massive companion on a similarly eccentric orbit can recreate a similar disk structure. Our results allude to such a companion being located around an orbital distance of 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.