Dynamical mass of a solar-like oscillator at the main-sequence turnoff from Gaia astrometry & ground-based spectroscopy

TL;DR

This study validates asteroseismic masses for a solar-like oscillator at the main-sequence turnoff by combining Gaia DR3 astrometry with ground-based SB2 spectroscopy, yielding dynamical masses $M_1^{\mathrm{dyn}}=0.993\pm0.046\,M_\odot$ and $M_2^{\mathrm{dyn}}=0.889\pm0.041\,M_\odot$. Spectroscopic disentangling provides orbital parameters, enabling a robust dynamical solution when merged with the Gaia inclination. Kepler photometry supplies the seismic constraints, with global seismology giving $\nu_{\max}$ and $\Delta\nu$ and individual-frequency modeling delivering $M_1^{\mathrm{IF}}=0.92\pm0.01\,M_\odot$, $R_1^{\mathrm{IF}}=1.38\pm0.01\,R_\odot$, and $A_1^{\mathrm{IF}}=11.20\pm0.55$ Gyr; the IF mass agrees with the dynamical mass within $1.2\sigma$ after accounting for systematics. The results provide an empirical benchmark for MS solar-like oscillators and highlight Gaia+SB2 spectroscopy as a scalable approach for validating asteroseismology, with PLATO’s future data expected to expand the sample. Together, these findings support the reliability of seismic masses on the MS and pave the way for widespread calibration of large-scale asteroseismic surveys.

Abstract

Asteroseismology is widely used for precise determining of masses of solar-like oscillating stars by performing individual-frequency modeling or applying homological scaling relations. However, these methods lack dynamical validation on the main sequence due to the absence of eclipsing double-lined binary system (SB2) as benchmark objects. By providing the orbital inclination, astrometric binary systems from ESA Gaia DR3 offer an abundant alternative for eclipsing systems. We present KIC693187 as the first SB2, hosting a solar-like oscillating post-main-sequence star with dynamical masses. By combining Gaia astrometry with spectroscopic obtained with the Las Cumbres Observatory network (LCO), we find $M_1^\mathrm{dyn}$=0.99$\pm$0.05$M_\odot$ and $M_2^\mathrm{dyn}$=0.89$\pm$0.04$M_\odot$ for the primary and secondary, respectively. Asteroseismic parameters were extracted from photometry of the NASA \Kepler satellite. The mass from individual frequency modeling is $M_1^\mathrm{IF}$=0.92$\pm$0.01$M_\odot$. Taking into account the systematic uncertainty of 0.04$M_\odot$ for best fit models from individual frequency fitting, we find an agreement within 1.2$σ$. From scaling relations we obtain a mass range of 0.93 to 0.98$M_\odot$ by using the observed large frequency separations (\dnu) in the scaling relations for the primary. By using standard corrections for departures from the asymptotic regime of \dnu, we obtained a mass range of 0.83 to 1.03$M_\odot$. The upper ends of both ranges agree well with the dynamical mass of the primary. This approach provides the first empirical validation for main-sequence solar-like oscillators and opens a new window for validating asteroseismology. Through a dedicatded program targeting astrometric SB2 binary systems, ESA's PLATO space mission will provide will enlarge the benchmark sample substantially.

Figures (6)

• Figure 1: Echelle diagram of the target for the observed (closed symbols) and modeled (open symbols) oscillation modes. Crosses mark the positions of the model frequencies, uncorrected for the surface effects.
• Figure 3: CCF profiles for KIC 9693187 as function of the orbital phase. The vertical line marks the systematic velocity of the system.
• Figure 5: Comparison of the spectral window before and after removing the long gap between Q1 and Q5 for KIC 9693187. In the top panel, the window functions of the original light curve (in blue) and of the light curve after long gap removal (in orange) are shown. The second panel shows the spectral windows in both cases, and the third panel presents a zoom on the first 10 bins of the PSD, as described in the text. The bottom panel shows the cumulative power of the spectral window for both cases.
• Figure 6: PSD of the primary of KIC 9693187. The multi-component fit to the PSD and (upper panel) and the power excess (lower panel) are shown. In the upper panel, the dash-dotted liens represent the background fits, while the dashed red line represents the gaussian fit. The solid line represents the combined fit to the PSD. The vertical dashes in the lower panel indicate the of the extracted radial (blue), dipole (dark red), and quadruple (orange). The solid red line depicts the combined solution of all extracted modes.
• Figure 7: PSD of KIC 9693187 around the excess of power spectral density. The top panel shows the full power excess, with the original, and smoothed PSD in grey, and black, respectively. The lower provides a zoomed view on the two central radial orders. The red line depicts the combined model of extracted frequencies, which are represented by the vertical dashes (blue, red, and orange for $\ell$=0, 1, and 2, resp., see Table \ref{['tab:individualFrequencies']}).