High-resolution infrared spectroscopy of the dust-obscured metal-poor open cluster Trumpler 5

¹ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
² Department of Astronomy and Space Sciences, Ege University, 35100 Bornova, İzmir, Türkiye
³ Department of Astronomy and McDonald Observatory, The University of Texas, Austin, TX 78712, USA
⁴ Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 2Y2, Canada
⁵ Dipartimento di Fisica e Astronomia “Galileo Galilei”, Univ. di Padova, Vicolo dell’Osservatorio 3, Padova 35122, Italy
⁶ Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-gu, Daejeon 34055, Republic of Korea

^★ Corresponding authors: sergen@camk.edu.pl; sergenozdemir58@gmail.com; melike.afsar@ege.edu.tr

Received: 10 October 2024
Accepted: 7 May 2025

Abstract

Context. Open clusters are important tools to investigate the chemistry of the Galactic disk. Trumpler 5 is a moderately old, dust-obscured metal-poor open cluster. In this study, high-resolution near-infrared spectroscopic data of seven giant stars from the Trumpler 5 cluster were analyzed to derive chemical abundances for 20 elements and ¹²C/¹³C ratios. A color-magnitude diagram (CMD) analysis of BV and Gaia photometry has also been performed for a comprehensive study of the cluster.

Aims. This work uses high-resolution near-infrared spectroscopy exclusively to derive atmospheric parameters and chemical abundances in the obscured open cluster Trumpler 5. Thanks to the methodology employed, some targets are studied for the first time. Additionally, it provides a detailed CMD analysis using photometric and spectroscopic data.

Methods. We gathered high-resolution spectra for seven Trumpler 5 red giants in the near-infrared H and K wavelength domains, using the Immersion Grating INfrared Spectrometer (IGRINS). Five out of seven targets have been studied for the first time here with high-resolution spectroscopy. We introduced a method to initially estimate the stellar surface gravity (log g) by using calibrated equivalent widths of the Ti II line at 15 873 Å from a large sample. We performed standard spectroscopic analyses to refine the model atmospheric parameters of our targets and determined the chemical abundances primarily through spectrum synthesis. We also performed CMD analyses to extract differential reddening correction to compare cluster parameters both with and without corrections.

Results. We derived stellar parameters for seven members of Trumpler 5 with our method and the results are consistent with both the literature and other methods. We also inferred elemental abundances for more than 20 species, along with the ¹²C/¹³C ratios. The elemental abundances are in good agreement with the literature values for similar targets. Through CMD analysis, we found the reddening value, E(B-V)≃0.76, and estimated the age of the cluster to be approximately 2.50 Gyr.