Letter to the Editor

Oscillations in the Sun with SONG: Setting the scale for asteroseismic investigations^⋆

¹ Stellar Astrophysics Centre, Aarhus University, 8000 Aarhus C, Denmark
e-mail: madsfa@phys.au.dk
² Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
³ Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
⁴ Department of Astronomy, China West Normal University, No 1 Shi Da Road, Nanchong City, Sichuan Province, PR China
⁵ Sydney Institute for Astronomy, School of Physics, University of Sydney, Camperdown, New South Wales 2006, Australia
⁶ Université Paris Diderot, AIM, Sorbonne Paris Cité, CEA, CNRS, 91191 Gif-sur-Yvette, France
⁷ IRFU, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
⁸ DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 328, 2800 Kgs. Lyngby, Denmark

Received: 31 January 2019
Accepted: 25 February 2019

Abstract

Context. We present the first high-cadence multiwavelength radial-velocity observations of the Sun-as-a-star, carried out during 57 consecutive days using the stellar échelle spectrograph at the Hertzsprung SONG Telescope operating at the Teide Observatory.

Aims. Our aim was to produce a high-quality data set and reference values for the global helioseismic parameters ν_max, ⊙ and Δν_⊙ of the solar p-modes using the SONG instrument. The obtained data set or the inferred values should then be used when the scaling relations are applied to other stars showing solar-like oscillations observed with SONG or similar instruments.

Methods. We used different approaches to analyse the power spectrum of the time series to determine ν_max, ⊙: simple Gaussian fitting and heavy smoothing of the power spectrum. We determined Δν_⊙ using the method of autocorrelation of the power spectrum. The amplitude per radial mode was determined using the method described in Kjeldsen et al. (2008, ApJ, 682, 1370).

Results. We found the following values for the solar oscillations using the SONG spectrograph: ν_max, ⊙ = 3141 ± 12 μHz, Δν_⊙ = 134.98 ± 0.04 μHz, and an average amplitude of the strongest radial modes of 16.6 ± 0.4 cm s⁻¹. These values are consistent with previous measurements with other techniques.