The curse

Gustafsson, Mai Lan

doi:10.1037/e719362011-019

Cited by 1 publication

(2 citation statements)

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“…In brief, there are two modules in E-iSpec: one for determining atmospheric parameters (using the equivalent width (EW) method, see Section 3.1) and the other for determining abundances (using EW and synthetic spectral fitting (SSF), see Section 3.2). For the spectral analyses, the latest LTE model atmospheres, ATLAS9 (Castelli & Kurucz 2003) or MARCS (Gustafsson et al 2008), chosen depending on the of the star, were used in combination with the LTE abundance calculation routine MOOG (version July 2009) by Sneden (1973). The model atmospheres were uniquely determined by the , , [Fe/H] and .…”

Section: Spectroscopic Analysismentioning

confidence: 99%

“…We derived chemical abundances using both the EW method and the SSF technique – which are modules of E-iSpec. In the EW method, observed EWs were compared with predictions from theoretical model atmospheres (ATLAS9 Castelli & Kurucz 2003 or MARCS Gustafsson et al 2008), involving an iterative adjustment of assumed abundances until observed and predicted EWs converged, yielding best-fit abundance values. The SSF technique involved comparing observed stellar spectra with synthetic spectra generated by theoretical model atmospheres, employing chi-square fitting to iteratively refine model parameters and derive precise chemical abundances.…”

Section: Spectroscopic Analysismentioning

confidence: 99%

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s-Process Enriched Evolved Binaries in the Galaxy and the Magellanic Clouds

Menon,

Kamath,

Mohorian

et al. 2024

Publ. Astron. Soc. Aust.

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Post-asymptotic giant branch stars (post-AGB) in binary systems, with typical orbital periods between ∼100 to ∼1000 days, result from a poorly understood interaction that terminates their precursory AGB phase. The majority of these binaries display a photospheric anomaly called ‘chemical depletion’, thought to arise froman interaction between the circumbinary disc and the post-AGB star, leading to the reaccretion of pure gas onto the star, devoid of refractory elements due to dust formation. In this paper, we focus on a subset of chemically peculiar binary post-AGBs in the Galaxy and the Magellanic Clouds (MCs). Our detailed stellar parameter and chemical abundance analysis utilising high-resolution optical spectra from VLT+UVES revealed that our targets span a Teff of 4900 - 7250K and [Fe/H] of -0.5 - -1.57 dex. Interestingly, these targets exhibit a carbon ([C/Fe] ranging from 0.5 - 1.0 dex, dependant on metallicity) and s-process enrichment ([s/Fe]≥1dex) contrary to the commonly observed chemical depletion pattern. Using spectral energy distribution (SED) fitting and period-luminosity-colour (PLC) relation methods, we determine the luminosity of the targets (2700 – 8300 L⊙), which enables confirmation of their evolutionary phase and estimation of initial masses (as a function of metallicity) (1 - 2.5M⊙). In conjunction with predictions from dedicated ATON stellar evolutionary models, our results indicate a predominant intrinsic enrichment of carbon and s-process elements in our binary post-AGB targets. We qualitatively rule out extrinsic enrichment and inherited s-process enrichment from the host galaxy as plausible explanations for the observed overabundances. Our chemically peculiar subset of intrinsic carbon and s-process enriched binary post-AGBs also hints at potential variation in the efficiency of chemical depletion between stars with C-rich and O-rich circumbinary disc chemistries. However, critical observational studies of circumbinary disc chemistry, along with specific condensation temperature estimates in C-rich environments, are necessary to address gaps in our current understanding of disc-binary interactions inducing chemical depletion in binary post-AGB systems.

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