Modeling Massive Stars with Rotation: the Case of Nitrogen Enrichments

TL;DR

This paper investigates nitrogen enrichment in massive stars, demonstrating that rotational mixing correlates with multiple stellar parameters when controlling for biases, including binary evolution effects.

Contribution

It introduces a multivariate model for nitrogen enrichment, clarifying the role of rotational mixing and addressing observational biases in massive star data.

Findings

Nitrogen enrichment correlates with mass, age, rotation velocity, and metallicity.

Binary evolution accounts for about 20% of nitrogen enrichment anomalies.

Controlling parameters supports the rotational mixing hypothesis.

Abstract

Recently, the concept of rotational mixing has been challenged by some authors (e.g. Hunter et al. 2008). We show that the excess N/H is a multivariate function f(M, age, v, sin i, multiplicity,Z). To find a correlation of a multivariate function with some parameter, it is evidently necessary to limit as much as possible the range of the other involved parameters. When this is done, the concept of rotational mixing is supported by the observations. We also show that the sample data are not free from several biases. A fraction of about 20% of the stars may escape to the relation as a result of binary evolution.