Testing the wavelength dependence of oscillation and granulation using Kepler and TESS

We have developed a new and fast method for measuring nu_max and the amplitude of oscillations. Unlike most other pipelines, we do not fit the granulation background. Instead, we simply divide the power spectrum by a function of the form nu^−2 and then smooth heavily to measure nu_max (Sreenivas et al., 2024). This procedure is able to measure oscillations in 99.9  percent of the 16,000 previously studied Kepler red giants, showing its ability to handle large datasets with low computational cost. On comparing the seismic radii from this work with Gaia, we see similar trends to those observed in previous studies. Additionally, our method can clearly identify the dipole-mode suppressed stars as a distinct population, and hence provide an efficient way to detect them. We also apply this method to red giants observed by TESS. These include about 6000 of the Kepler red giants, as well as many thousands of brighter red giants in the TESS Continuous Viewing Zones (CVZs). We compare the amplitudes of oscillation and granulation in TESS and Kepler to measure the wavelength dependence, which is important information for the upcoming Roman mission (which will observe in the near infrared). We investigate how the method used for light curve extraction affects the amplitudes we observe,
and we define metrics to indicate significant detection of oscillations in low signal-to-noise case.