Probing the Mass-Loss History of VY CMa

Övrigt konferensbidrag, 2008

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 (MZAMS ⪆ 8 Msun) 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 (˜ 2.8 × 10-4 Msun/yr) some 1000 yr ago, lasting some 100 yr, followed by a low mass-loss phase (˜ 1 × 10-6 Msun/yr) taking some 800 yr. The current mass-loss rate is estimated to be in the order of 1 × 10-4 Msun/yr.