“…The three targets are J005107 from the SMC (Kamath et al 2014), MACHO 47.2496.8 from the LMC (Reyniers & Cuypers 2005), and HD 158616 (De Smedt et al 2016) from the Galaxy. We note that HD 158616 is a confirmed binary according to orbital parameter studies conducted by Oomen et al (2018). With regards to J005107 and MACHO 47.2496.8, taking into account a combination of their SED characteristics and pulsation features (as detailed below for each of the targets), we conclude that these two stars also reside in binary systems. Figure 1. The WISE colour-colour diagram for the sample stars along with the stars studied in Gezer et al (2015) is depicted here.…”
Section: Targets and Observationssupporting
confidence: 58%
“…Additionally, the high-resolution spectroscopic studies by Rao et al (2012) and De Smedt et al (2016) established HD 158616 as the first post-AGB star rich in s -process elements discovered to be in a spectroscopic binary. HD 158616 is confirmed to be a binary star with an orbital period of 365.0 days, and additional orbital properties can be found in Oomen et al (2018). De Smedt et al (2016) also identified this star as a disc-source due to a characteristic IR excess in its SED.…”
Section: Targets and Observationsmentioning
confidence: 70%
“…Hence, we provide the mean value of each measurement in Table 2. We refer to the Appendix A of Oomen et al (2018) for the list of the most common catalogues used.…”
Section: Targets and Observationsmentioning
confidence: 99%
“…Observational studies have now firmly established that the presence of the stable compact disc (circumbinary disc) around the disc-sources is attributed to their binary nature (e.g. Van Winckel et al 2009; Oomen et al 2018; Kluska et al 2022).…”
Section: Introductionmentioning
confidence: 99%
“…Additionally, the majority of the post-AGB stars in binary systems (disc-sources) exhibit a chemical anomaly in their photosphere known as ‘chemical depletion’ (see Oomen et al 2018; Kamath & Van Winckel 2019, and references therein). This phenomenon arises from the interaction between the binary post-AGB star and the surrounding circumbinary disc (disc-binary interaction).…”
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.
“…The three targets are J005107 from the SMC (Kamath et al 2014), MACHO 47.2496.8 from the LMC (Reyniers & Cuypers 2005), and HD 158616 (De Smedt et al 2016) from the Galaxy. We note that HD 158616 is a confirmed binary according to orbital parameter studies conducted by Oomen et al (2018). With regards to J005107 and MACHO 47.2496.8, taking into account a combination of their SED characteristics and pulsation features (as detailed below for each of the targets), we conclude that these two stars also reside in binary systems. Figure 1. The WISE colour-colour diagram for the sample stars along with the stars studied in Gezer et al (2015) is depicted here.…”
Section: Targets and Observationssupporting
confidence: 58%
“…Additionally, the high-resolution spectroscopic studies by Rao et al (2012) and De Smedt et al (2016) established HD 158616 as the first post-AGB star rich in s -process elements discovered to be in a spectroscopic binary. HD 158616 is confirmed to be a binary star with an orbital period of 365.0 days, and additional orbital properties can be found in Oomen et al (2018). De Smedt et al (2016) also identified this star as a disc-source due to a characteristic IR excess in its SED.…”
Section: Targets and Observationsmentioning
confidence: 70%
“…Hence, we provide the mean value of each measurement in Table 2. We refer to the Appendix A of Oomen et al (2018) for the list of the most common catalogues used.…”
Section: Targets and Observationsmentioning
confidence: 99%
“…Observational studies have now firmly established that the presence of the stable compact disc (circumbinary disc) around the disc-sources is attributed to their binary nature (e.g. Van Winckel et al 2009; Oomen et al 2018; Kluska et al 2022).…”
Section: Introductionmentioning
confidence: 99%
“…Additionally, the majority of the post-AGB stars in binary systems (disc-sources) exhibit a chemical anomaly in their photosphere known as ‘chemical depletion’ (see Oomen et al 2018; Kamath & Van Winckel 2019, and references therein). This phenomenon arises from the interaction between the binary post-AGB star and the surrounding circumbinary disc (disc-binary interaction).…”
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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