${}^{12}$CO Ro-vibrational Spectroscopy of AB Aurigae -- A Potential Point Source is Present

TL;DR

This study uses M-band spectroscopy to identify a potential new point source in the AB Aurigae system, distinct from known features, suggesting the presence of an unknown companion possibly with a circumplanetary disk.

Contribution

First detection of a compact, off-centered source in AB Aurigae using ${}^{12}$CO ro-vibrational spectroscopy, indicating a potential new companion in the system.

Findings

Localized a low-temperature, compact source at 65 au from the star.

Source's position differs from the known protoplanet AB Aur b.

Estimated temperature of the source is about 550 K with a radius of 5 au.

Abstract

The Herbig Ae star AB Aurigae hosts a vast, low-inclination protoplanetary disk that exhibits a plethora of substructures, including the protoplanet candidate AB Aur b. We present M-band spectroscopic data taken with NASA IRTF from Feb 2024 covering multiple position angles that captured emission from an off-centered, low temperature, and compact source. Analysis of the ${}^{12}$CO $\nu=$1-0 low-J ro-vibrational emission line profiles and spectroastrometric signals localizes the source at around an orbital radius of 65 au and a position angle of 143$^\circ$. These coordinates are distinctly different from those of AB Aur b, which was not detected. Although there is no obvious explanation for the detected source, if we assume it was a circumplanetary disk, then its maximum temperature would be about 550 K and its maximum radius would be about 5 au. Our results alludes to a previously unknown companion that may be residing in the AB Aurigae system.