Chemical depletion in the Large Magellanic Cloud: RV Tauri stars and the photospheric feedback from their dusty discs

TL;DR

This study investigates chemical depletion in RV Tauri stars in the Large Magellanic Cloud, revealing that depletion patterns are common and linked to stable dusty discs, similar to Galactic counterparts, with implications for binary systems and disc evolution.

Contribution

First detailed analysis of depletion patterns and circumstellar environments of LMC RV Tauri stars, establishing their similarity to Galactic post-AGB binaries with dusty discs.

Findings

Depletion patterns are common in LMC RV Tauri stars.

Depletion is closely related to the presence of stable Keplerian discs.

Some sources show evidence of evolved or debris discs.

Abstract

Aims: By studying the photospheric abundances of 4 RV Tauri stars in the LMC, we test whether the depletion pattern of refractory elements, seen in similar Galactic sources, is also common for extragalactic sources. Since this depletion process probably only occurs through interaction with a stable disc, we investigate the circumstellar environment of these sources. Methods: A detailed photospheric abundance study was performed using high-resolution UVES optical spectra. To study the circumstellar environment we use photometric data to construct the spectral energy distributions of the stars, and determine the geometry of the circumstellar environment, whereas low-resolution Spitzer-IRS infrared spectra are used to trace its mineralogy. Results: Our results show that, also in the LMC, the photospheres of RV Tauri stars are commonly affected by the depletion process, although it can differ significantly in strength from source to source. From our detailed disc modelling and mineralogy study, we find that this process, as in the Galaxy, appears closely related to the presence of a stable Keplerian disc. The newly studied extragalactic objects have similar observational characteristics as Galactic post-AGB binaries surrounded by a dusty disc, and are therefore also believed to be part of a binary system. One source shows a very small infrared excess, atypical for a disc source, but still has evidence for depletion. We speculate this could point to the presence of a very evolved disc, similar to debris discs seen around young stellar objects.