Researchers determine chemical composition of two extremely metal-poor stars | 5/15/2018 | Staff
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Top panel: Fe abundances derived from all lines, as a function of the lower excitation potential, for the adopted model for SDSS J0826+6125. Lower panel: Fe abundances, as a function of reduced equivalent widths, for the measured lines. Credit: Bandyopadhyay et al., 2018.

A group of scientists led by Avrajit Bandyopadhyay of the Indian Institute of Astrophysics, Bangalore, has conducted chemical analysis of two bright, extremely metal-poor stars. The results of the analysis, presented May 6 in a paper published on, provide important insights into the nature of these stars, and could help astronomers better understand their origin.

Stars - Subject - Study - SDSS - J082625

The stars that are the subject of the study are designated SDSS J082625.70+612515.10 and SDSS J134144.60+474128.90. The two stars were identified by the SDSS-MARVELS spectroscopic pre-survey as extremely metal-poor, with iron to hydrogen abundance ratios of –3.1 and –3.2 respectively.

Bandyopadhyay's team observed both stars with the Hanle Echelle Spectrograph (HESP) on the 2.3-m Himalayan Chandra telescope (HCT) at the Indian Astronomical Observatory (IAO) in India. The observational campaign, conducted between November 2015 and November 2016, allowed the astronomers to obtain essential information about the chemical composition of the two objects.

Paper - Science - Results - HESP - Analysis

"In this paper, the first science results using HESP, we present a detailed analysis of their chemical abundances," the paper reads.

According to the study, SDSS J082625.70+612515.10 (SDSS J0826+6125 for short), with an apparent magnitude of 11.44 and an effective temperature of 4,300 K, has a chemical composition generally consistent with stars in halo of our Milky Way galaxy. It turns out that this star is carbon-enhanced and exhibits depletion in nitrogen, what could be due to internal mixing within the star. Moreover, the...
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