IRAS\,11472-0800: an extremely depleted pulsating binary post-AGB star

Abstract

We focus here on one particular and poorly studied object, IRAS11472-0800. It is a highly evolved post-Asymptotic Giant Branch (post-AGB) star of spectral type F, with a large infrared excess produced by thermal emission of circumstellar dust. We deploy a multi-wavelength study which includes the analyses of optical and IR spectra as well as a variability study based on photometric and spectroscopic time-series. The spectral energy distribution (SED) properties as well as the highly processed silicate N-band emission show that the dust in IRAS11472-0800 is likely trapped in a stable disc. The energetics of the SED and the colour variability show that our viewing angle is close to edge-on and that the optical flux is dominated by scattered light. With photospheric abundances of [Fe/H] = -2.7 and [Sc/H]=-4.2, we discovered that IRAS11472-0800 is one of the most chemically-depleted objects known to date. Moreover, IRAS11472-0800 is a pulsating star with a period of 31.16 days and a peak-to-peak amplitude of 0.6 mag in V. The radial velocity variability is strongly influenced by the pulsations, but the significant cycle-to-cycle variability is systematic on a longer time scale, which we interpret as evidence for binary motion. We conclude that IRAS11472-0800 is a pulsating binary star surrounded by a circumbinary disc. The line-of-sight towards the object lies close the the orbital plane making that the optical light is dominated by scattered light. IRAS11472-0800 is one of the most chemically-depleted objects known so far and links the dusty RV\,Tauri stars to the non-pulsating class of strongly depleted objects.

12 pages, 14 figures Accepted for publication in A&A Main Journal

References in corpus (7)

• Keplerian discs around post-AGB stars: a common phenomenon?
• Silicate features in Galactic and extragalactic post-AGB discs
• SPITZER survey of dust grain processing in stable discs around binary post-AGB stars
• Defining the instability strip of pulsating post-AGB binary stars from ASAS and NSVS photometry
• Dust-grain processing in circumbinary discs around evolved binaries. The RV Tauri spectral twins RU Cen and AC Her
• First detection of photospheric depletion in the LMC
• A Spectroscopic and Photometric Study of the Metal-Poor, Pulsating, Post-AGB Binary HD 46703

Cited by in corpus (6)

• Modelling depletion by re-accretion of gas from a dusty disc in post-AGB stars
• An interferometric study of the post-AGB binary 89 Herculis I Spatially resolving the continuum circumstellar environment at optical and near-IR wavelengths with the VLTI, NPOI, IOTA, PTI, and the CHARA Array
• Multi-band polarimetry of post-asymptotic giant branch stars stars. Optical measurements
• High-resolution spectroscopy of the extremely iron-poor post-AGB star CC Lyr
• Variability and possible rapid evolution of the hot post-AGB stars Hen 3-1347, Hen 3-1428, and LSS 4634
• Modelling the impact of circumbinary disk accretion on post-AGB binary evolution and surface chemistry