The (B0+?)+O6 system FN CMa: A case for tidal-pulsational interaction?

TL;DR

This study analyzes the binary system FN CMa, revealing tidal interactions potentially affecting pulsations, through high-resolution spectroscopy and disentangling of the system's components, and suggests a link between orbital eccentricity and stellar variability.

Contribution

It provides the first detailed spectroscopic analysis of FN CMa, identifying component A as an SB1 binary with a 117.55-day period and evidence of tidal-pulsational interaction.

Findings

Component A is an SB1 binary with a 117.55-day orbit.

Rapid line-profile variations indicate pulsations in component A.

Eccentricity of 0.6 suggests possible tidal modulation of pulsations.

Abstract

FN CMa is visually double with a separation of about 0.6arcsec. Sixty high-cadence VLT/UVES spectra permit the A and B components to be disentangled, as the relative contribution of each star to the total light entering the spectrograph fluctuates between exposures due to changes in seeing. Component A exhibits rapid line-profile variations, leading us to attribute the photometric variability seen by HIPPARCOS (with a derived P=0.08866d) to this component. From a total of 122 archival and new echelle spectra it is shown that component A is an SB1 binary with an orbital period of 117.55 days. The eccentricity of 0.6 may result in tidal modulation of the pulsation(s) of component Aa.