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 12CO ν=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∘. 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.
@article{arxiv.2603.00250,
title = {${}^{12}$CO Ro-vibrational Spectroscopy of AB Aurigae -- A Potential Point Source is Present},
author = {Janus Kozdon and Jeffrey Fung and Sean D. Brittain and Stanley Jensen and Josh Kern and Cory Padgett and Yasuhiro Hasegawa},
journal= {arXiv preprint arXiv:2603.00250},
year = {2026}
}