Astronomy:HE 1327-2326

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Short description: Very low metallicity star in the constellation Hydra
HE 1327-2326
HE1327-2326Location.png
Location of HE 1327-2326 (circled in red)
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Hydra
Right ascension  13h 30m 05.940s[1]
Declination −23° 41′ 49.70″[1]
Apparent magnitude (V) 13.5[2]
Astrometry
Proper motion (μ) RA: -52.524±0.040[1] mas/yr
Dec.: 45.498±0.035[1] mas/yr
Parallax (π)0.8879[1] ± 0.0235[1] mas
Distance3673+100
−95[1] ly
(1126+30
−29[1] pc)
Details
Mass0.7[3] M☉
Temperature6,180[3] K
Metallicity[math]\displaystyle{ \begin{smallmatrix}\left[\ce{Fe}/\ce{H}\right]\end{smallmatrix} }[/math] = −5.4±0.2[2]
Other designations
SPM3.2 4266486, 2MASS J13300595-2341497, Gaia DR2 6194815228636688768[4]
Database references
SIMBADdata

HE 1327-2326, discovered in 2005 by Anna Frebel and collaborators,[2] was the star with the lowest known iron abundance until SMSS J031300.36−670839.3 was discovered.[5] The star is a member of Population II stars, with a solar-standardised iron to hydrogen index [Fe/H], or metallicity, of −5.4±0.2. The scale being logarithmic, this number indicates that its iron content is about 1/250000 that of the Earth's sun. However, it has a carbon abundance of roughly one-tenth solar ([C/H] = −1.0), and it is not known how these two abundances can have been produced/exist simultaneously. Discovered by the Hamburg/ESO survey for metal-poor stars, it was probably formed during an age of the universe when the metal content was much lower. It has been speculated that this star is part of the second generation, born out of the gas clouds which were imbued with elements such as carbon by the primordial Population III stars.[6]

As of 2018, HE 1327-2326 was the brightest star known with [Fe/H] < -5. This is important because the spectral lines for metals are weak in such stars, so a bright star is needed to obtain high signal/noise spectra.[3]

The small amount of metals seen in HE 1327-2326 are believed to have been produced by a supernova event in a first generation star. Spherically symmetric models of supernovae fail to reproduce the relative abundances of metals seen in HE 1327-2326, regardless of the mass of the supernova progenitor. Because of this, Ezzeddine et al. argued in 2019 that HE 1327-2326's metal enrichment was due to an aspherical supernova explosion of a 25 M☉ Population III star which enriched the interstellar medium via mass loss through bipolar jets.[6]

See also

Ultra low metallicity / ultra metal poor stars

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  2. ↑ 2.0 2.1 2.2 Frebel A.; Aoki W.; Christlieb N.; Ando H.; Asplund M.; Barklem P.S.; Beers T.C.; Eriksson K. et al. (14 April 2005). "Nucleosynthetic signatures of the first stars". Nature 434 (7035): 871–873. doi:10.1038/nature03455. PMID 15829957. Bibcode: 2005Natur.434..871F. 
  3. ↑ 3.0 3.1 3.2 Ezzeddine, Rana; Frebel, Anna (August 2018). "Revisiting the Iron Abundance in the Hyper Iron-poor Star HE 1327-2326 with UV COS/HST Data". The Astrophysical Journal 863 (2): 168. doi:10.3847/1538-4357/aad3cb. Bibcode: 2018ApJ...863..168E. 
  4. ↑ "HE 1327-2326". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HE+1327-2326. 
  5. ↑ Brainard, Curtis (10 February 2014). "The Archaeology of the Stars". New York Times. https://www.nytimes.com/2014/02/11/science/space/the-archaeology-of-the-stars.html. 
  6. ↑ 6.0 6.1 Ezzeddine, Rana; Frebel, Anna; Roederer, Ian U.; Tominaga, Nozomu; Tumlinson, Jason; Ishigaki, Miho; Nomoto, Ken'ichi; Placco, Vinicius M. et al. (May 2019). "Evidence for an Aspherical Population III Supernova Explosion Inferred from the Hyper-metal-poor Star HE 1327-2326". The Astrophysical Journal 876 (2): 97. doi:10.3847/1538-4357/ab14e7. Bibcode: 2019ApJ...876...97E. 

External links



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