Standing on the shoulders of Dwarfs: the Kepler asteroseismic LEGACY sample II - radii, masses, and ages (1611.08776v3)

Abstract: We use asteroseismic data from the Kepler satellite to determine fundamental stellar properties of the 66 main-sequence targets observed for at least one full year by the mission. We distributed tens of individual oscillation frequencies extracted from the time series of each star among seven modelling teams who applied different methods to determine radii, masses, and ages for all stars in the sample. Comparisons among the different results reveal a good level of agreement in all stellar properties, which is remarkable considering the variety of codes, input physics and analysis methods employed by the different teams. Average uncertainties are of the order of $\sim$2\% in radius, $\sim$4\% in mass, and $\sim$10\% in age, making this the best-characterised sample of main-sequence stars available to date. Our predicted initial abundances and mixing-length parameters are checked against inferences from chemical enrichment laws $\Delta Y / \Delta Z$ and predictions from 3D atmospheric simulations. We test the accuracy of the determined stellar properties by comparing them to the Sun, angular diameter measurements, Gaia parallaxes, and binary evolution, finding excellent agreement in all cases and further confirming the robustness of asteroseismically-determined physical parameters of stars when individual frequencies of oscillation are available. Baptised as the Kepler dwarfs LEGACY sample, these stars are the solar-like oscillators with the best asteroseismic properties available for at least another decade. All data used in this analysis and the resulting stellar parameters are made publicly available for the community.

A Comprehensive Study of Main-Sequence Stellar Properties Using Asteroseismology from the Kepler LEGACY Sample

The Kepler space mission's asteroseismic data has enabled the precise characterization of main-sequence stars, as discussed in Silva Aguirre et al.'s paper, using data from 66 stars observed for at least one year. The paper utilizes individual oscillation frequencies analyzed by various modeling teams to determine crucial stellar properties—radii, masses, and ages—with impressive precision: approximately 2% for radii, 4% for masses, and 10% for ages.

Methodology and Results

This paper employs an extensive asteroseismology approach, leveraging multiple modeling pipelines:

• Data Utilization: Teams used tens of oscillation frequencies and combined these with classical parameters (effective temperature and metallicity) to provide comprehensive modeling.
• Pipeline Analysis: Seven distinct pipelines, each employing different evolutionary and pulsation codes and fitting methods, processed the data to derive stellar properties. Despite employing varied methods, the resulting stellar properties showed a remarkable consensus, indicating robustness in asteroseismology when individual frequencies are available.

Comparisons and Validation

The paper conducted several verifications to ensure the accuracy of the derived stellar properties:

• Consistency Across Pipelines: The results were cross-validated by comparing outputs from different modeling techniques. Generally, the pipelines showed strong agreement, though some systematic and proportional biases were observed, related to differing codes or physical assumptions.
• Empirical Validation: Stellar property estimates were cross-validated with independent measurements, including solar parameters, interferometry, and Gaia parallaxes. The paper demonstrated that asteroseismic results are largely consistent with empirical observations, lending further credibility to asteroseismic methods in determining stellar properties.

Implications for Stellar Astrophysics

The paper provides valuable benchmarks for the solar-like oscillators in the galaxy, with implications extending to fields such as Galactic Archeology. The high-precision characterization of stars aids significantly in tests of stellar evolutionary models and theories regarding stellar interiors. Moreover, a deep comparison is made with theoretical predictions from 3D hydrodynamical simulations, suggesting directions for refinement in stellar modeling, particularly regarding convective efficiency and initial helium abundance.

Future Directions

While confirming the precision of asteroseismology in determining stellar properties, the paper also opens further avenues for studies leveraging these well-characterized stars. Such studies might focus on aspects like surface helium abundance via stellar oscillations, tests of mixing-length parameters using atmospheric simulations, or dynamic inferences of stellar interiors. Additionally, with missions like PLATO on the horizon, this sample sets a foundational comparative standard for future explorations in astrophysics.

In conclusion, the paper delivers a robust analysis leveraging an unprecedented dataset to affirm the precision of asteroseismically derived stellar parameters, opening pathways for refined modeling and understanding of stellar phenomena. Such studies will undoubtedly enrich our comprehension of stellar evolution and the broader galactic structure.