Solar-like oscillations in the metal-poor subgiant nu Indi: II. Acoustic spectrum and mode lifetime

TL;DR

This study uses asteroseismology to analyze the internal structure of the metal-poor subgiant star nu Indi by examining its acoustic spectrum and mode lifetimes through extensive velocity measurements.

Contribution

It provides detailed seismic analysis of nu Indi, identifying multiple oscillation modes and measuring their properties, including a notably long mode damping time.

Findings

Identified 13 oscillation modes between 200 and 500 uHz.

Measured mode damping time of approximately 16 days.

Detected regular frequency spacings indicating internal stellar structure.

Abstract

Convection in stars excites resonant acoustic waves which depend on the sound speed inside the star, which in turn depends on properties of the stellar interior. Therefore, asteroseismology is an unrivaled method to probe the internal structure of a star. We made a seismic study of the metal-poor subgiant star nu Indi with the goal of constraining its interior structure. Our study is based on a time series of 1201 radial velocity measurements spread over 14 nights obtained from two sites, Siding Spring Observatory in Australia and ESO La Silla Observatory in Chile. The power spectrum of the high precision velocity time series clearly presents several identifiable peaks between 200 and 500 uHz showing regularity with a large and small spacing of 25.14 +- 0.09 uHz and 2.96 +- 0.22 uHz at 330 uHz. Thirteen individual modes have been identified with amplitudes in the range 53 to 173 cm/s. The mode damping time is estimated to be about 16 days (1-sigma range between 9 and 50 days), substantially longer than in other stars like the Sun, the alpha Cen system or the giant xi Hya.