Detection of a new star greatly improved by the r-process

admin October 07, 2024

Comparison of high-resolution spectra of J 0206+4941 and a moderately r-process enhanced (rI) star, HD 124897 ([Eu/Fe] = +0.45, with similar stellar parameters. Credit: Xie et al., 2024.

Using the Gran Telescopio Canarias (GTC) telescope, astronomers from the Chinese Academy of Sciences (CAS) and elsewhere have discovered a new star that is extremely enhanced by the r-process in the thin disk of the Milky Way. The discovery was reported in a research paper published July 16 on the preprint server arXiv.

Enhanced r-process (ERP) stars represent a small fraction of old metal-poor stars that exhibit large increases in elements (such as europium, thorium, or uranium) produced during the rapid neutron capture process. These stars, which mainly populate the galactic halo and the dwarf satellite galaxies of the Milky Way, are excellent laboratories for studying the r-process and could help us better understand the assembly history of our galaxy.

A team of astronomers led by Xiao-Jin Xie of CAS recently announced the detection of a new RPE star. They used the GTC’s High-Resolution Optical Spectrograph (HORuS) to observe a star called LAMOST J020623.21+494127.9 (or J 0206+4941 for short). The observation campaign led to the classification of this object as an extremely r-process enhanced star.

“He [J 0206+4941] “It was initially selected from the medium-resolution LAMOST survey as a candidate RPE star, due to its unusually strong europium lines,” the researchers wrote in the paper.

Observations revealed that J 0206+4941 is a bright star that belongs to the thin disk of the Milky Way. Based on the collected data, astronomers were able to deduce the abundances of 30 elements in this star and determine its kinematics.

According to the new findings, J 0206+4941 has a metallicity of -0.54, an effective temperature of about 4078 K, and an abundance ratio of europium to hydrogen of 0.78. In general, the abundances of light elements in this star were found to be comparable to those of other stars of similar metallicity and evolutionary phase, with a large increase in europium and a modest increase in barium.

The authors of the paper point out that J 0206+4941 is therefore the most metal-rich and highly r-process enhanced star discovered to date. The age of the star is uncertain, probably around 12.3 billion years, and further studies are needed to confirm this.

In an attempt to explain the origin of J 0206+4941, scientists do not rule out the possibility that it was born in situ in the thin disk of the Milky Way. They add that it could have formed from an interstellar medium (ISM) enriched in r-process elements by a merger of binary neutron stars or by a core-collapsed supernova (CCSNe).

In conclusion, the astronomers noted that in addition to J 0206+4941, they also identified a few other metal-rich RPE candidates that deserve further study using instruments such as HORuS.

More information:

Xiao-Jin Xie et al., Discovery of an extremely r-process enhanced thin disk star with [Eu/H] = +0.78, arXiv (2024). DOI: 10.48550/arxiv.2407.11572

Journal information:

arXiv

Quote:A new star extremely enhanced by the r process has been detected (2024, July 23) retrieved July 23, 2024 from https://phys.org/news/2024-07-extremely-star.html

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