Issue |
A&A
Volume 690, October 2024
|
|
---|---|---|
Article Number | A327 | |
Number of page(s) | 6 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361/202451473 | |
Published online | 21 October 2024 |
Testing the asteroseismic estimates of stellar radii with surface brightness-colour relations and Gaia DR3 parallaxes
Red giants and red clump stars
1
Dipartimento di Fisica “Enrico Fermi”, Università di Pisa, Largo Pontecorvo 3, 56127
Pisa, Italy
2
INFN, Sezione di Pisa, Largo Pontecorvo 3, 56127
Pisa, Italy
Received:
12
July
2024
Accepted:
9
September
2024
Aims. We compared stellar radii derived from asteroseismic scaling relations with those estimated using two independent surface brightness-colour relations (SBCRs) combined with Gaia DR3 parallaxes.
Methods. We cross-matched asteroseismic and astrometric data for over 6400 red giant branch (RGB) and red clump (RC) stars from the APO-K2 catalogue with the TESS Input Catalogue v8.2 to obtain precise V band magnitudes and E(B − V) colour excesses. We then adopted two different SBCRs from the literature to derive stellar radius estimates, denoted as Ra and Rb, respectively. We analysed the ratio of these SBCR-derived radii to the asteroseismic radius estimates, R, provided in the APO-K2 catalogue.
Results. Both SBCRs exhibited good agreement with asteroseismic radius estimates. On average, Ra was overestimated by 1.2% with respect to R, while Rb was underestimated by 2.5%. For stars larger than 20 R⊙, SBCR radii are systematically lower than asteroseismic ones. The dispersion in the radius ratio was similar for the two methods (around 10%). The agreement with asteroseismic radii shows a strong dependence on the parallax. The dispersion is halved for stars with a parallax greater than 2.5 mas. In this subsample, Rb showed perfect agreement with R, while Ra remained slightly overestimated, by 3%. A trend with [Fe/H] was found at a level of 4% to 6% per dex. Additionally, a clear trend with asteroseismic mass is found. For stars less massive than about 0.95 M⊙, SBCR radii were significantly higher than asteroseismic ones, by about 6%. This overestimation correlated with the presence of extended helium cores in these stars’ structures relative to their envelopes. Furthermore, radius ratios showed a dichotomous behaviour at higher masses, mainly due to the presence of several RC stars with SBCR radii significantly lower with respect to asteroseismology. This behaviour originates from a different response of asteroseismic scaling relations and SBCR to [α/Fe] abundance ratios for massive stars, both in RGB and RC phases, which is reported here for the first time.
Key words: methods: statistical / stars: evolution / stars: fundamental parameters / stars: interiors
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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