Unique distant classical Cepheid OGLE GD-CEP-1353 with anomalously high abundances of s- and r-process elements

¹ Astronomical Observatory, Odessa National University, Shevchenko Park, 65014 Odessa, Ukraine
e-mail: andrievskii@ukr.net
² Institut für Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
³ GEPI, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, 92190 Meudon, France
⁴ Physics of stars department, Crimean Astrophysical Observatory, Nauchny 298409, Crimea

Received: 7 August 2023
Accepted: 20 September 2023

Abstract

Aims. While looking for recently discovered distant Cepheids with an interesting chemical composition, we noticed one star (OGLE GD-CEP-1353) with extremely large equivalent widths of spectral lines of heavy elements. The aim of this work is to perform an abundance analysis, and to find a possible explanation for the found chemical anomaly.

Methods. Quantitative analysis of the equivalent widths and synthetic spectrum synthesis were used to derive abundances in this star. Both local and nonlocal thermodynamic equilibrium (LTE and NLTE) approximations were used in our analysis.

Results. Abundances of 28 chemical elements from carbon to thorium were derived. While light and iron peak elements show abundances typical for distant Cepheids (located in the outer disk), the s-process elements are overabundant about one dex. r-process elements are slightly less overabundant. This makes the star a unique Cepheid of our Galaxy.