Detection prospects of solar $g$-modes with LISA

Abstract

The possibility of detecting solar oscillation modes using space-based gravitational-wave detectors has been investigated in the context of gravitational-wave interferometry, with Polnarev \cite{Polnarev:2009xf} demonstrating that low-frequency solar modes could, in principle, produce detectable signals in a LISA-type interferometer. Motivated by this work, I revisit the problem using current solar models, updated detector sensitivities, and improved theoretical and observational constraints on mode amplitudes. In this study, I compute the gravitational response of solar oscillation modes using standard solar models generated with \texttt{MESA}, and mode eigenfrequencies and eigenfunctions calculated with \texttt{GYRE}. I focus primarily on solar $g$ modes, evaluating their responses for degree $l=2$ and azimuthal orders $m=0$ and $m=2$. The analysis incorporates both the earlier proposed and the current updated LISA sensitivity curves, and I perform a comparative assessment with the TianQin mission in the relevant low-frequency band. To assess the robustness of the predicted signals, I estimate the gravitational responses using two different standard solar models based on the GS98 and AGSS09 abundance compilations. I find that the resulting signal responses are nearly identical for the two models, indicating that uncertainties in solar metallicity have a negligible impact on the detectability of solar $g$ modes by space-based interferometers.

Figures (5)

• Figure 1: Comparison of the $g$ mode frequencies from the Updated MESA GS98, Updated MESA AGSS09 models and Polnarev:2009xf values. The first 22 solar $g$ modes are shown, along with the fractional differences relative to the models.
• Figure 2: Comparison of the quadrupole moment $J_2$ values for solar $g$ modes from the Updated MESA GS98, Updated MESA AGSS09 models and Polnarev:2009xf values. The first 22 solar $g$ modes are shown, along with the fractional differences relative to the models.
• Figure 3: Projected response of the $S_0$ and $S_2$ for a signal-to-noise ratio (SNR) of 3 in velocity-based experiments, shown for the LISA and TianQin sensitivities. The gravitational-wave signals are computed using the Updated MESA GS98 and Updated MESA AGSS09 solar models, assuming an observational upper bound on the $g$-mode velocity amplitude. Signals corresponding to theoretically predicted velocity amplitudes are also included. For comparison, results are shown for both the originally proposed and the current updated LISA sensitivity curves.
• Figure 4: Projected near-zone (solid lines) and far-zone (dashed lines) responses of the $S_0$ and $S_2$ modes for the Updated MESA GS98 solar model, assuming a signal-to-noise ratio (SNR) of 3 in velocity-based experiments. The responses are shown for the LISA and TianQin sensitivities. For comparison, results corresponding to both the originally proposed and the current updated LISA sensitivity curves are included.
• Figure 5: Comparison of the signal-to-noise ratio ($S/N$) for LISA as a function of frequency for solar oscillation modes with $\ell=2$ and $m=2$. The $S/N$ is evaluated assuming a detection threshold of $S/N=3$ for solar velocity measurements and using the theoretically predicted velocity amplitudes from Ref. Balmforth_1992MNRAS.255..639B. The solid blue curve shows the $S/N$ including instrumental noise only, while the dashed red curve includes both instrumental noise and Galactic binary confusion noise for the velocity-based upper-limit amplitudes. For the theoretically predicted amplitudes, the solid black curve corresponds to instrumental noise only, and the dashed green curve includes both instrumental and confusion noise.