2020ApJ...889..138S

We have mapped the young Herbig Be star R Mon in CO(3-2) and ¹³CO(3-2) with Atacama Pathfinder EXperiment in Chile and analyzed unpublished Herschel images. We find that R Mon is embedded in a small cloud with a gas temperature of ∼20 K and a total mass of ∼70 M_☉. We confirm that R Mon drives a bipolar molecular outflow, which is blueshifted north of R Mon. The blueshifted outflow has excavated the molecular cloud north of R Mon, creating the reflection nebula NGC 2261 and filling it with high-velocity gas. At "high" velocities the orientation of the outflow is approximately n-s, which agrees with the optical jet, suggesting that the accretion disk is e-w. The outflow velocities are modest, ±9 km s^–1. The outflow is rather massive, ∼0.56 M_☉ in the blueshifted outflow lobe. The outflow is completely optically thick in CO(3-2) toward R Mon, indicating that its envelope is <=2000 au. The mass of the accretion disk and surrounding envelope determined from an isothermal graybody fit is ∼0.34 M_☉. We estimate a mass-loss rate of ∼(1-3) x 10^–5 M_☉ yr^–1, corresponding to an accretion rate of (1-9) x 10^–6 M_☉ yr^–1. We find that R Mon has bolometric luminosity of <1000 L_☉. R Mon is still in an active accretion phase, contributing to the observed luminosity. Hence, R Mon cannot be a B0 star; it must be a late B star or even an early A star.