Astronomy Unit Seminar - Leen Decin

When: Friday, January 29, 2021, 2:30 PM - 3:30 PM
Where: Online event

Speaker: Leen Decin (KU Leuven)

The ALMA ATOMIUM Large Program: (Sub)stellar companions shape the winds of evolved stars

The ALMA Large Program ATOMIUM[1] is the first observational campaign of a large sample of oxygen-rich Asymptotic Giant Branch (AGB) stellar winds at high angular resolution and sensitivity. In this talk, we present one of the early successes of ATOMIUM which was published in Science in September 2020. Planetary nebulae (PNe) are well-known to reveal a wide range of morphologies. Bipolarity is the main characteristic, but jets and tori are also detected. Several contending theories of the evolution from a (roughly) spherically symmetric Asymptotic Giant Branch (AGB) stellar wind to a very non-spherical PN have emerged. Here, we present the first observational proof that (sub)stellar binary activity – including the effects of planets, brown dwarfs, and low-mass stellar companions -  is the dominant shaping mechanism of AGB stellar winds, and their successors the PNe. We show that low mass-loss rate oxygen-rich AGB winds are more readily prone to complex structural deformations owing to their slow wind acceleration, whereas a binary-induced spiral structure is more prevalent in other classes of AGB stellar winds. These results resolve several previously unexplained phenomena — including the absence of detached shells around oxygen-rich AGB stars and disks around carbon-rich PNe — and have critical implications for the formation of type Ia supernovae. Our results also imply that the effects of planets around evolved stars are more easily detected in early-type oxygen-rich AGB stars.

[1] ATOMIUM refers to the ALMA Cycle 6 Large Project in Band 6, ALMA Tracing the Origins of Molecules formIng dUst in oxygen-rich M-type stars