Uncovering the pulsating photospheres of Mira stars through near-IR interferometry: a case study on R Vir

TL;DR

This study uses near-infrared interferometry data to analyze the pulsating photospheres and molecular layers of Mira stars, focusing on R Vir, revealing insights into their dynamic atmospheres over multiple pulsation cycles.

Contribution

It introduces a methodology combining archival and new interferometric data with a sinusoidal model to study Mira star atmospheres across pulsation cycles.

Findings

Preliminary evidence of pulsation-driven changes in stellar and layer diameters.

Correlation between photospheric and molecular layer variations.

Validation of the sinusoidal model for Mira star atmospheres.

Abstract

We present the methodology and some preliminary results of our study of the relationship between a Mira's pulsating photosphere and its surrounding molecular layer(s) throughout several pulsation cycles, based on spatially resolved data. Our dataset consists of archival narrow-band observations in the near-infrared H and K bands obtained with the Palomar Testbed Interferometer between 1999 and 2006, extended with a few nights of VLTI AMBER low spectral resolution data and near-infrared SAAO photometry. The fitted model is the geometric star + layer model proposed by Perrin et al. (2004), in which the physical parameters (diameter and temperature of star and layer; wavelength dependent optical depth of the layer) are given a sinusoidal time dependence.