Austrian Early Career Conference 2024

Contribution:
Poster

Authors:
Andrei-Alexandru Cristea

Affiliations:
Institute of Science and Technology Austria (ISTA)

Title:
Astro-cardiology: can binary-stripped stars be used to trace the spins of cores in evolved massive stars?

Abstract:
Stellar rotation is thought to be responsible for strong interior chemical mixing, especially in low-metallicity stars, and to directly relate with the spins of the black holes and neutron stars they result in. However, angular momentum transport inside stars and the formation of dynamo magnetic field structures remain poorly understood. Despite this, binary systems may provide valuable insight. In binary systems, stripping of the hydrogen-rich envelope will expose the helium core, thus providing the possibility to trace the core rotation of evolved massive stars directly from the surfaces of these stripped donor stars. We compare a series of single and He-rich stripped binary evolutionary models, that we computed with the 1D stellar evolution code MESA. The rotation profiles of single red super-giant (RSG) models employing the Tayler-Spruit dynamo are characterized by differential rotation, with a rapidly rotating rigid core (omega~2.158e-4 rad/s) and a slowly rotating rigid envelope (omega~4.13e-10 rad/s). This indicates that the core and envelope are magnetically weakly bound and rotationally decouple shortly after the main sequence. This is in agreement with our binary-stripped star models: their final spins are negligibly affected by the loss of their hydrogen-rich envelopes and their angular momentum profiles closely map those of the single RSG cores. This suggests that the surface rotation rates of binary-stripped stars may be used as proxies for core rotations of evolved massive stars. A comparison of our models with new observations of binary stripped stars could produce a first set of direct observational constraints on angular momentum processes happening inside evolved massive stars.