Abstract:
We present for the first time the detection of mid-J CO line emission in the outskirts of an evolved massive star, which indicates the presence of warm and/or high-density molecular gas. Aiming to learn about the interplay between evolved massive stars and their surroundings, we have carried out CO J = 2→ 1, J = 3→ 2, and 13↑CO J = 2→ 1 line observations in a 4' × 4' field around the ring nebula G79.29+0.46, which is illuminated by a strong LBV star candidate. The whole field shows extended predominant emission in both CO and 13↑CO J = 2→ 1 lines, which probably comes from the large cloud which contains the star-forming region DR 15. When this large-scale emission is removed, minor-scale features become evident, particularly in the CO J = 3→ 2 line, strikingly coincident with the ring nebula. The high critical density of CO J = 3→ 2 (some 10↑4 cm↑−3) gives additional support for the association with the massive star, since high-density molecular gas has more chances to survive in such a harsh environment. This structure may have been produced by the cumulative effect of a strong steady wind in the LBV stage or earlier, which has compressed the surviving parent molecular cloud. In addition, immer...