Astronomers identify a mega metal-poor dwarf star

February 27, 2018 by Tomasz Nowakowski, Phys.org report
Upper panel: ISIS spectrum of J0023+0307 and J1029+1729 (black line) and the best fits obtained with FERRE (red line). The bottom panels show a details of the Ca II H & K region (a) and the G-band (b), respectively. Main stellar parameters are shown. Image credit: Aguado et al., 2018.

A group of Spanish astronomers has found a new primitive mega metal-poor star. The object, designated SDSS J0023+0307, is apparently one of the most iron-poor stars known to date. The finding is reported February 17 in a paper published on the arXiv pre-print repository.

Metal-poor stars are rare objects as only few stars with abundances [Fe/H] below –5 have been discovered so far. Currently, SMSS J0313–6708, with metallicity below –7.1, is the most iron-poor star known to date. Astronomers are interested in expanding the still short list of metal-poor stars as such objects have the potential to improve our knowledge of the chemical evolution of the universe.

During recent years, a team of astronomers led by David S. Aguado of the Institute of Astrophysics in the Canary Islands, has been searching for extremely metal-poor stars by analyzing low-resolution spectroscopic data provided by various instruments. This search has already resulted in finding a carbon-enhanced metal-poor red giant with iron abundance of -4.7 and a dwarf star with iron abundance below –5.8.

Now, Aguado's team found an extremely metal-poor candidate in the SDSS/BOSS spectroscopic survey. Next, they conducted follow-up observations of this candidate using the Intermediate dispersion Spectrograph and Imaging System (ISIS) on the 4.2m William Herschel Telescope (WHT) and the Optical System for Imaging and low-intermediate-Resolution Integrated Spectroscopy (OSIRIS) at the Gran Telescopio Canarias (GTC).

"We have now identified a new mega metal-poor dwarf with [Fe/H]< −6.6, J0023+0307, from SDSS/BOSS spectra (λ/∆λ ~2, 000). Follow-up spectroscopy with the 10.4m GTC and the 4.2m WHT telescopes confirms the metallicity determination based on SDSS data," the researchers wrote in the paper.

As noted in the study, the newly detected metal-poor star, named SDSS J0023+0307, has an iron abundance below –6.6. Moreover, the astronomers found that this star has a carbon abundance below 6.3 and an effective temperature of 6,188 K.

Although the scientists were only able to set upper limits for the iron and carbon abundances of SDSS J0023+0307, the results indicate that this object is one of the two most iron-poor stars known, and exhibits less carbon that most of stars with iron abundances below –5.

"The spectrum of this star does not show the usual enhancement in carbon found in all other stars at [Fe/H]< −5," the paper reads.

The authors of the paper noted that given that the iron abundance is only an upper limit, and since carbon does not appear enhanced at the levels found in other hyper metal-poor stars, J0023+0307 could well be the most metal-poor star so far identified. However, more observations at higher resolution and signal-to-noise ratio are required to validate this assumption.

"Newer observations with higher spectral resolution and very high signal-to-noise ratio are required and can only be obtained with the largest telescopes in the world," the researchers concluded.

Explore further: Researchers discover a chemically primitive dwarf star in the galactic halo

More information: J0023+0307: A MEGA METAL-POOR DWARF STAR FROM SDSS/BOSS, arxiv.org/pdf/1802.06240.pdf

Related Stories

The most metal-poor dwarf star-forming galaxy found

September 5, 2017

(Phys.org)—Using the Large Binocular Telescope (LBT), a group of astronomers has found that the star-forming galaxy (SFG) J0811+4730 is the most metal-poor dwarf SFG known to date. The finding is detailed in a paper published ...

First PEPSI data release

January 9, 2018

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first batch of high-spectral resolution data to the scientific community. In a series of ...

Recommended for you

The surprising environment of an enigmatic neutron star

September 17, 2018

An unusual infrared emission detected by the Hubble Space Telescope from a nearby neutron star could indicate that the pulsar has features never before seen. The observation, by a team of researchers at Penn State, Sabanci ...

Ceres takes life an ice volcano at a time

September 17, 2018

Every year throughout its 4.5-billion-year life, ice volcanoes on the dwarf planet Ceres generate enough material on average to fill a movie theater, according to a new study led by the University of Arizona.

Slowest-spinning radio pulsar detected by astronomers

September 17, 2018

An international team of astronomers has discovered a new radio pulsar as part of the LOFAR Tied-Array All-Sky Survey (LOTAAS). The newly detected object, designated PSR J0250+5854, turns out to be the slowest-spinning radio ...

3 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

rubiks6
1 / 5 (1) Feb 27, 2018
What is the mass of the star? (What type is it?)
What is the distance of the star?
Is there an estimate for the age of the star?
Is anything known about the galactic environment around the star?

A low-metallicity star must have formed from a low-metallicity primordial cloud which shouldn't exist 13.8 billion years after the big bang.

This "discovery" is fraught with problems and missing information. The source for this article. arXiv, is a non-peer reviewed rag.
rrwillsj
1 / 5 (1) Feb 28, 2018
Good questions rubik6.

It is my opinion (without any supporting evidence) that the cosmos is a lot more of a kludgefest of randomized chaos then we are willing to admit.

This star wound up in the low end of the curve. Missing out on collecting materials compared against the average observed star.
Just the way the dice bounced. Corpolites happen!
jonesdave
3.4 / 5 (5) Feb 28, 2018
This "discovery" is fraught with problems and missing information. The source for this article. arXiv, is a non-peer reviewed rag.


First off, Arxiv is usually fine. Yes, you do get some unpublished stuff on there, but it is mostly used as a pre-print server for papers that have been accepted in decent journals. A quick search on this paper shows that it was published in ApJ:
http://iopscience...db8/meta

Maybe you were thinking of vixra?

The age of the star is thought to be ~ 13.8 Gyrs, from:
http://www.iac.es...;lang=en

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.