Searching for solar-like oscillations in the delta Scuti star rho Puppis

TL;DR

This study conducted a detailed spectroscopic campaign on rho Puppis to search for solar-like oscillations, but found no such oscillations above 0.5 m/s amplitude, despite theoretical predictions of their existence.

Contribution

The paper presents the first high-resolution spectroscopic search for solar-like oscillations in a delta Scuti star, using iodine cell technique and multi-site data collection.

Findings

No solar-like oscillations detected above 0.5 m/s amplitude.

Radial velocity amplitudes vary among spectral lines.

The dominant delta Scuti pulsation mode is the radial fundamental.

Abstract

Despite the shallow convective envelopes of delta Scuti pulsators, solar-like oscillations are theoretically predicted to be excited in those stars as well. To search for such stochastic oscillations we organised a spectroscopic multi-site campaign for the bright, metal-rich delta Sct star rho Puppis. We obtained a total of 2763 high-resolution spectra using four telescopes. We discuss the reduction and analysis with the iodine cell technique, developed for searching for low-amplitude radial velocity variations, in the presence of high-amplitude variability. Furthermore, we have determined the angular diameter of rho Puppis to be 1.68 \pm 0.03 mas, translating into a radius of 3.52 \pm 0.07Rsun. Using this value, the frequency of maximum power of possible solar-like oscillations, is expected at ~43 \pm 2 c/d (498 \pm 23 muHz). The dominant delta Scuti-type pulsation mode of rho Puppis is known to be the radial fundamental mode which allows us to determine the mean density of the star, and therefore an expected large frequency separation of 2.73 c/d (31.6 muHz). We conclude that 1) the radial velocity amplitudes of the delta Scuti pulsations are different for different spectral lines; 2) we can exclude solar-like oscillations to be present in rho Puppis with an amplitude per radial mode larger than 0.5 m/s.