The G+M eclipsing binary V530 Orionis: A stringent test of magnetic stellar evolution models for low-mass stars

TL;DR

This study uses detailed observations of the V530 Ori binary system to test and validate magnetic stellar evolution models for low-mass stars, addressing longstanding discrepancies in stellar radius and temperature predictions.

Contribution

It provides precise measurements of stellar parameters and demonstrates that magnetic models can accurately reproduce observed properties of low-mass stars.

Findings

Standard models underpredict radius and overpredict temperature of the secondary.

Magnetic models from Dartmouth match observations at 3 Gyr with realistic magnetic field strengths.

Observations suggest magnetic fields have a small effect on the primary star's properties.

Abstract

We report extensive photometric and spectroscopic observations of the 6.1-day period, G+M-type detached double-lined eclipsing binary V530 Ori, an important new benchmark system for testing stellar evolution models for low-mass stars. We determine accurate masses and radii for the components with errors of 0.7% and 1.3%, as follows: M(A) = 1.0038 +/- 0.0066 M(sun), M(B) = 0.5955 +/- 0.0022 M(sun), R(A) = 0.980 +/- 0.013 R(sun), and R(B) = 0.5873 +/- 0.0067 R(sun). The effective temperatures are 5890 +/- 100 K (G1V) and 3880 +/- 120 K (M1V), respectively. A detailed chemical analysis probing more than 20 elements in the primary spectrum shows the system to have a slightly subsolar abundance, with [Fe/H] = -0.12 +/- 0.08. A comparison with theory reveals that standard models underpredict the radius and overpredict the temperature of the secondary, as has been found previously for other M dwarfs. On the other hand, models from the Dartmouth series incorporating magnetic fields are able to match the observations of the secondary star at the same age as the primary (3 Gyr) with a surface field strength of 2.1 +/- 0.4 kG when using a rotational dynamo prescription, or 1.3 +/- 0.4 kG with a turbulent dynamo approach, not far from our empirical estimate for this star of 0.83 +/- 0.65 kG. The observations are most consistent with magnetic fields playing only a small role in changing the global properties of the primary. The V530 Ori system thus provides an important demonstration that recent advances in modeling appear to be on the right track to explain the long-standing problem of radius inflation and temperature suppression in low-mass stars.