The study probes the chemical composition of the metal-poor star HD 1936.

Evolutionary status of HD 1936. Credit: Çalışkan et al, 2024

Using the Ankara University Kraken Observatory (AUKR) in Turkey, astronomers have made high-resolution spectroscopic observations of a metal-poor star known as HD 1936. The results of the observation campaign, published February 15 on the preprint server arXivshed more light on the chemical composition of this star.

Metal-poor stars are rare objects because there are only a few thousand iron-rich stars. [Fe/H] Below -2.0 have been discovered to date. Expanding the still short list of And studying these objects in detail is of great value to astronomers, as such stars have the potential to improve our knowledge of the chemical evolution of the universe.

HD 1936 (also known as HIP 1873) is a very bright metal-poor star of spectral type G5, located about 1,000 light-years away in the galactic halo. The star, which is about 10 billion years old, is estimated to be at least 10 times more massive than the Sun, while its mass is likely to be between 0.9 and 3.0 solar masses. Some studies have suggested that the star has a substellar companion with a mass of about 18.35 Jupiters.

Although previous observations determined the atmospheric parameters of HD 1936, a detailed chemical study of the star has not yet been performed. That is why a team of Turkish astronomers led by Ankara University’s Şeyma Çalışkan decided to investigate HD 1936 with the Hopeschel Spectrograph mounted on AUKR’s 0.8-m Berhiteddin Albayrak telescope.

“We present a high resolution and high SNR based chemical abundance of the extremely bright metal-poor star HD 1936. [signal-to-] spectra from AUKR,” the researchers wrote.

Team HD was able to obtain the abundances of 29 atomic species for 1936. The star’s metallicity was determined to be on the order of -1.74, which is generally in agreement with previous estimates.

The observations revealed that HD 1936 is not carbon-enhanced and exhibits luminosities as well as od-Z element abundance ratios consistent with most metal-weak field stars. The sodium-to-iron abundance ratio appears to be subsolar, while the aluminum-to-iron abundance ratio turns out to be supersolar.

According to the paper, the initial lithium abundance for HD 1936 was about 1.01 dex. This is consistent with what is typically seen in stars of the lower red giant branch.

The determined abundance ratios of europium and barium suggested very little S-process contamination for the probe star. He allowed it. Classifying HD 1936 as a moderately r-process-enhanced metal-poor star.

The obtained results also suggest that HD 1936 may be a second-generation star that formed in a multiphase environment. The measured abundance ratios of magnesium and carbon due to multiple supernovae indicate enrichment.

More information:
Şeyma Çalışkan et al., Chemical Composition of the Evolved Very Bright Metal-Poor Star HD 1936, arXiv (2024). DOI: 10.48550/arxiv.2402.09840

Journal Information:

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Reference: Study probes chemical composition of metal-poor star HD 1936 (2024, Feb 22) Accessed 22 Feb 2024 at https://phys.org/news/2024-02-chemical-composition-metal-poor-star.html Obtained from

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