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Spectroscopy of a sample of RV Tauri stars without IR excess

Karlis Pukitis, Karina Korenika

TL;DR

The study investigates chemical depletion in RV Tauri stars lacking IR excess to understand disc evolution and binary interactions in evolved stars. Using high-resolution optical spectroscopy and LTE abundance analysis anchored by Fe excitation/ionization balance, the authors derive photospheric parameters and elemental abundances for five targets, with ASAS-SN photometry to place the spectra in pulsation phase. They find no depletion in HD 172810, V399 Cyg, or AA Ari, while V457 Cyg shows a depletion pattern consistent with accretion from a dissipated circumbinary disc and TiO emission, suggesting a binary with remnants of a disc. V894 Per appears contaminated by a companion, complicating the abundance analysis, but shows a notable Na overabundance likely tied to binary mass transfer. Overall, the results demonstrate that depletion can occur in RV Tauri stars without IR excess, offering insights into disc longevity, binary interactions, and the past presence of circumbinary material in evolved stars.

Abstract

We observed high-resolution optical spectra of 11 RV Tauri stars without IR excess, with the primary goal of searching for chemical depletion patterns. Using equivalent widths of absorption lines, we calculated photospheric parameters and chemical element abundances for five stars in the sample: HD 172810, V399 Cyg, AA Ari, V457 Cyg, and V894 Per. Only the abundance pattern of V457 Cyg suggests depletion. In the spectrum of this star, TiO lines are also observed in emission in addition to metal emissions. V457 Cyg is likely a binary system that was once surrounded by a circumbinary disc. In the spectrum of V894 Per, we find a set of spectral lines that appear to belong to another star, corroborating that it is an eclipsing variable rather than an RV Tauri star. The high overabundance of sodium may result from mass transfer within the binary system.

Spectroscopy of a sample of RV Tauri stars without IR excess

TL;DR

The study investigates chemical depletion in RV Tauri stars lacking IR excess to understand disc evolution and binary interactions in evolved stars. Using high-resolution optical spectroscopy and LTE abundance analysis anchored by Fe excitation/ionization balance, the authors derive photospheric parameters and elemental abundances for five targets, with ASAS-SN photometry to place the spectra in pulsation phase. They find no depletion in HD 172810, V399 Cyg, or AA Ari, while V457 Cyg shows a depletion pattern consistent with accretion from a dissipated circumbinary disc and TiO emission, suggesting a binary with remnants of a disc. V894 Per appears contaminated by a companion, complicating the abundance analysis, but shows a notable Na overabundance likely tied to binary mass transfer. Overall, the results demonstrate that depletion can occur in RV Tauri stars without IR excess, offering insights into disc longevity, binary interactions, and the past presence of circumbinary material in evolved stars.

Abstract

We observed high-resolution optical spectra of 11 RV Tauri stars without IR excess, with the primary goal of searching for chemical depletion patterns. Using equivalent widths of absorption lines, we calculated photospheric parameters and chemical element abundances for five stars in the sample: HD 172810, V399 Cyg, AA Ari, V457 Cyg, and V894 Per. Only the abundance pattern of V457 Cyg suggests depletion. In the spectrum of this star, TiO lines are also observed in emission in addition to metal emissions. V457 Cyg is likely a binary system that was once surrounded by a circumbinary disc. In the spectrum of V894 Per, we find a set of spectral lines that appear to belong to another star, corroborating that it is an eclipsing variable rather than an RV Tauri star. The high overabundance of sodium may result from mass transfer within the binary system.
Paper Structure (7 sections, 5 figures, 3 tables)

This paper contains 7 sections, 5 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Observations
  3. Analysis
  4. Results and Discussion
  5. HD 172810, V399 Cyg, and AA Ari
  6. V457 Cyg
  7. V894 Per

Figures (5)

  • Figure S1: The ASAS-SN light curves of V399 Cyg, V457 Cyg, and V894 Per. The grey vertical lines indicate the times of the spectroscopic observations.
  • Figure S2: Photospheric abundances of V457 Cyg as a function of condensation temperature, using values from Lodders2003. Vertical lines indicate the standard deviation of the calculated abundances.
  • Figure S3: Photospheric abundances of V457 Cyg as a function of the FIP.
  • Figure S4: Region of the spectrum of V457 Cyg where emission lines are clearly visible. The strongest absorption and emission lines are identified with black vertical lines, while grey vertical lines correspond to the wavelengths of the TiO spectral lines.
  • Figure S5: Region of the spectrum of V894 Per where two sets of absorption lines are clearly visible. The most intense spectral lines, corresponding to a radial velocity of -64.3 km/s, are identified with black vertical lines. To the left of these lines, the same absorptions, corresponding to a radial velocity of approximately -137 km/s, are marked.