Probing the Mass-Loss History of VY CMa

Mass loss plays a dominant role in the evolution of low-mass stars while they are on the Asymptotic Giant Branch (AGB). Recent studies have hinted towards the importance of time variability of the mass-loss rates of such objects. Likewise, more massive stars (M_ZAMS ⪆ 8 M_o) may pass through a red supergiant phase and lose mass in a similar manner. By modelling the full line profiles of low excitation CO transitions emitted in the circumstellar envelope (CSE), we have studied the mass-loss history of the well-studied supergiant VY CMa. We show that this source underwent a phase of high mass loss (Ëœ2.8 × 10^-4 M_o/yr) some 1000 yr ago. This phase lasted some 100 yr, and was followed by a low mass-loss phase (Ëœ 1 × 10^-6 M_o/yr) taking some 800 yr. The current mass-loss rate is estimated to be on the order of 1 × 10^-4 M_o/yr.