Solar cycle variation of $\hat{I}{½}_{\max }$ in helioseismic data and its implications for asteroseismology

Abstract

The frequency, $\hat{I}{½}_{\max }$, at which the envelope of pulsation power peaks for solar-like oscillators is an important quantity in asteroseismology. We measure $\hat{I}{½}_{\max }$ for the Sun using 25 years of Sun-as-a-Star Doppler velocity observations with the Birmingham Solar-Oscillations Network (BiSON), by fitting a simple model to binned power spectra of the data. We also apply the fit to Sun-as-a-Star Doppler velocity data from GONG and GOLF, and photometry data from VIRGO/SPM on the ESA/NASA SOHO spacecraft. We discover a weak but nevertheless significant positive correlation of the solar $\hat{I}{½}_{\max }$ with solar activity. The uncovered shift between low and high activity, of $\simeq 25\hat{\mathrm{I}}¼\mathrm{Hz}$, translates to an uncertainty of 0.8 per cent in radius and 2.4 per cent in mass, based on direct use of asteroseismic scaling relations calibrated to the Sun. The mean $\hat{I}{½}_{\max }$ in the different datasets is also clearly offset in frequency. Our results flag the need for caution when using $\hat{I}{½}_{\max }$ in asteroseismology.

6 pages, 4 figures, published in MNRAS Letters, 2020, vol 493, pages L49 - 53 Corrected error in metadata list of authors