UV, IR, and mm Studies of CO Surrounding the Red Supergiant α Orionis (M2 Iab)

Carbon monoxide has been detected in Betelgeuse’s ultraviolet (electronic), infrared (vibrational), and mm‐radio (rotational) spectra, but its spatial distribution has remained elusive. We have obtained new mm‐radio interferometry (CARMA), infrared spatially‐resolved spectra (Phoenix/Gemini‐South), and we have performed non‐LTE simulations to help establish the spatial location of the S1 $(V = 10 km/s)$ and S2 $(V = 17 km/s)$ CO shells. The strong CO Fourth‐Positive ultraviolet scattering signature is apparent in the HST GHRS G140L spectrum and the S1 and S2 shells account for much of the UV opacity. Phoenix spectra reveal that the low velocity S1 shell is present at 1.5 arcsec West of the star and extends out to $∼4 arcsec,$ and its mm‐radio emission appears to originate within an 6 arcsec radius. The interpretation of the S2 shell is less clear. The Phoenix spectra tentatively suggest that the S2 shell extends to $∼7 arcsec.$ The CARMA channel maps show an additional strong narrow emission component 5 arcsec from the star, but the spectra do not show all the expected S1 and S2 signatures. Future CARMA observations should help to disentangle the signature of the S1 and S2 shells.