Searching for g modes: Part I. A new calibration of the GOLF instrument

TL;DR

This paper presents a new calibration method for 22 years of GOLF data, improving the consistency of p-mode amplitude measurements and time shift corrections, aiding the search for g modes in the Sun.

Contribution

It introduces a simplified calibration approach using only the spacecraft's radial velocity, enhancing data consistency for g-mode detection efforts.

Findings

Calibration aligns GOLF data with other instruments within a few percent.

Time shifts are within ±5 seconds for 99.8% of the data.

Improved calibration supports more reliable g-mode searches.

Abstract

The recent claims of g-mode detection have restarted the search for these potentially extremely important modes. These claims can be reassessed in view of the different data sets available from the SoHO instruments and ground-based instruments. We produce a new calibration of the GOLF data with a more consistent p-mode amplitude and a more consistent time shift correction compared to the time series used in the past. The calibration of 22 years of GOLF data is done with a simpler approach that uses only the predictive radial velocity of the SoHO spacecraft as a reference. Using p modes, we measure and correct the time shift between ground- and space-based instruments and the GOLF instrument. The p-mode velocity calibration is now consistent to within a few percent with other instruments. The remaining time shifts are within $\pm$ 5 s for 99.8% of the time series. Accepted by A&A on June 29, 2018