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E. Çelik

Publications and source records attributed to E. Çelik.

2 recordsLinked to original sources

Investigating Potential Relationships Between Mass Transfer Indicators and $δ$ Scuti Pulsations in oEA Systems

We explored potential associations between ongoing mass transfer and the pulsation properties of $δ$ Scuti primaries in a sample of 17 oscillating eclipsing Algol systems. For this purpose, we combined binary modelling, updated O-C analyses, and frequency characterization based on TESS photometry. To ensure homogeneity, the $T_{\rm eff}$ of the components were derived using a consistent SED fitting approach. From the binary solutions and O-C diagrams, we determined the mass transfer indicators (Q, dP/dt, and dM/dt) and examined their relations with the dominant pulsation period and amplitude. For the full sample, the results indicate weak to moderate positive trends, with the strongest relation found between logdP/dt and logPpuls, while the relations involving dM/dt and pulsation amplitudes are weaker and statistically insignificant. After excluding the two prominent outliers, R CMa and BW Del, the correlations between logPpuls and the mass transfer indicators become statistically more significant, including relations with dP/dt, Q, and dM/dt under both conservative and non-conservative assumptions. These relationships may reflect the indirect effects of mass transfer on the structure of the accreting primary and on the orbital configuration, potentially reducing tidal constraints and allowing shifts toward longer pulsation periods. However, the large dispersion and limited sample size indicate that these relationships remain poorly constrained. Our results suggest that pulsation properties are primarily governed by intrinsic stellar parameters and the well established Porb-Ppuls relation, while ongoing mass transfer may contribute as a secondary factor. Although the present sample does not allow firm conclusions regarding the role of mass transfer, this study provides a homogeneous observational framework for future investigations based on larger samples and improved constraints.

astro-ph.SR↗

A Homogeneous Spectroscopic and Evolutionary Study of cool HgMn and hot Metallic A Stars

We present a homogeneous spectroscopic and evolutionary analysis of chemically peculiar stars, focusing on HgMn and metallic A (Am) subclasses. Particular emphasis was placed on the coolest HgMn stars and the hottest Am stars, motivated by the long-standing hypothesis that these objects may represent consecutive evolutionary stages of a similar stellar population. High-resolution spectra of 13 HgMn and 14 Am targets were analyzed to derive atmospheric parameters and detailed chemical abundances. While all HgMn stars were confirmed to retain their chemically peculiar nature, only six of the fourteen candidate Am stars exhibit abundance patterns consistent with genuine Am characteristics, highlighting the importance of homogeneous spectroscopic classification. We investigate the temperature dependence of elemental abundances, finding a positive correlation between Mn abundance and $T_{\rm eff}$ and a negative correlation for Ni, supporting the operation of atomic diffusion. Stellar evolutionary models were computed with the MESA code using atmospheric parameters derived from the spectroscopic analysis. The locations of the confirmed HgMn and Am stars in the Hertzsprung--Russell diagram support the possibility that the cool HgMn stars and the hot Am stars may occupy overlapping evolutionary sequences. Although only a limited number of candidate pairs were identified, further analyses using evolutionary models that include atomic diffusion are needed to test the possible connection between the two subclasses.

astro-ph.SR↗