The onset of the AGB wind tied to a transition between sequences in the period-luminosity diagram. (arXiv:1901.06325v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+McDonald_I/0/1/0/all/0/1">Iain McDonald</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Trabucchi_M/0/1/0/all/0/1">Michele Trabucchi</a>
We link the onset of pulsation-enhanced, dust-driven winds from asymptotic
giant branch (AGB) stars in the Magellanic Clouds to the star’s transition
between period–luminosity sequences (from B to C’). This transition occurs at
~60 days for solar-mass stars, which represent the bulk of the AGB population:
this is the same period at which copious dust production starts in
solar-neighbourhood AGB stars. It is contemporaneous with the onset of
long-secondary period (LSP) variability on sequence D. The combined amplitude
of the first-overtone (B+C’) and fundamental (C) modes and (perhaps)
long-secondary period (D; LSP) variability appears to drive a sudden increase
in mass-loss rate to a stable plateau, previously identified to be a few x
10^-7 solar masses per year. We cite this as evidence that pulsations are
necessary to initiate mass loss from AGB stars and that these pulsations are
significant in controlling stars’ mass-loss rates. We also show evidence that
LSPs may evolve from long to short periods as the star evolves, counter to the
other period-luminosity sequences.
We link the onset of pulsation-enhanced, dust-driven winds from asymptotic
giant branch (AGB) stars in the Magellanic Clouds to the star’s transition
between period–luminosity sequences (from B to C’). This transition occurs at
~60 days for solar-mass stars, which represent the bulk of the AGB population:
this is the same period at which copious dust production starts in
solar-neighbourhood AGB stars. It is contemporaneous with the onset of
long-secondary period (LSP) variability on sequence D. The combined amplitude
of the first-overtone (B+C’) and fundamental (C) modes and (perhaps)
long-secondary period (D; LSP) variability appears to drive a sudden increase
in mass-loss rate to a stable plateau, previously identified to be a few x
10^-7 solar masses per year. We cite this as evidence that pulsations are
necessary to initiate mass loss from AGB stars and that these pulsations are
significant in controlling stars’ mass-loss rates. We also show evidence that
LSPs may evolve from long to short periods as the star evolves, counter to the
other period-luminosity sequences.
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