Unexpectedly large mass loss during the thermal pulse cycle of the red giant R Sculptoris!

TL;DR

This study reveals that during a thermal pulse, the red giant R Sculptoris loses significantly more mass than previously estimated, with a binary system structure influencing the mass-loss process.

Contribution

The paper provides observational evidence and hydrodynamic modeling showing unexpectedly large mass loss during thermal pulses in R Sculptoris, a binary star system.

Findings

Mass loss during the thermal pulse was about 0.003 solar masses.

A spiral structure indicates a binary companion influences the envelope.

Mass-loss rate increased by a factor of approximately 30 during the pulse.

Abstract

The asymptotic giant branch star R Sculptoris is surrounded by a detached shell of dust and gas. The shell originates from a thermal pulse during which the star undergoes a brief period of increased mass loss. It has hitherto been impossible to constrain observationally the timescales and mass-loss properties during and after a thermal pulse - parameters that determine the lifetime on the asymptotic giant branch and the amount of elements returned by the star. Here we report observations of CO emission from the circumstellar envelope and shell around R Sculptoris with an angular resolution of 1.3 arcsec. What was hitherto thought to be only a thin, spherical shell with a clumpy structure, is revealed to contain a spiral structure. Spiral structures associated with circumstellar envelopes have been seen previously, from which it was concluded that the systems must be binaries. Using the data, combined with hydrodynamic simulations, we conclude that R Sculptoris is a binary system that underwent a thermal pulse approximately 1800 years ago, lasting approximately 200 years. About 0.003 Msun of mass was ejected at a velocity of 14.3 km s-1 and at a rate approximately 30 times higher than the prepulse mass-loss rate. This shows that approximately 3 times more mass is returned to the interstellar medium during and immediately after a pulse than previously thought.