The amplitude of solar oscillations using stellar techniques

TL;DR

This study measures solar oscillation amplitudes using stellar techniques, compares them with helioseismology data, and provides a calibration method to improve theoretical models of stellar oscillations.

Contribution

It offers the first detailed calibration of solar oscillation amplitudes using stellar techniques and introduces an equation to estimate measurement uncertainties for other stars.

Findings

Mean solar amplitude for radial modes is 18.7 +/- 0.7 cm/s.

Mean solar amplitude for l=1 modes is 25.2 +/- 0.9 cm/s.

Provided amplitudes for three additional stars and revised values for five others.

Abstract

The amplitudes of solar-like oscillations depend on the excitation and damping, both of which are controlled by convection. Comparing observations with theory should therefore improve our understanding of the underlying physics. However, theoretical models invariably compute oscillation amplitudes relative to the Sun, and it is therefore vital to have a good calibration of the solar amplitude using stellar techniques. We have used daytime spectra of the Sun, obtained with HARPS and UCLES, to measure the solar oscillations and made a detailed comparison with observations using the BiSON helioseismology instrument. We find that the mean solar amplitude measured using stellar techniques, averaged over one full solar cycle, is 18.7 +/- 0.7 cm/s for the strongest radial modes (l=0) and 25.2 +/- 0.9 cm/s for l=1. In addition, we use simulations to establish an equation that estimates the uncertainty of amplitude measurements that are made of other stars, given that the mode lifetime is known. Finally, we also give amplitudes of solar-like oscillations for three stars that we measured from a series of short observations with HARPS (gamma Ser, beta Aql and alpha For), together with revised amplitudes for five other stars for which we have previously published results (alpha Cen A, alpha Cen B, beta Hyi, nu Ind and delta Pav).