Astronomy:Eta Scorpii

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Short description: Binary star in the constellation Scorpius

η Scorpii
Location of η Sco (circled)
Observation data
{{#ifeq:J2000|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| Epoch J2000      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000}}
Constellation Scorpius
η Sco A
Right ascension  17h 12m 09.19565s[1]
Declination −43° 14′ 21.0905″[1]
Apparent magnitude (V) 3.33[2]
η Sco B
Right ascension  17h 12m 51.49828s[3]
Declination −43° 20′ 31.0692″[3]
Apparent magnitude (V) 11.23±0.01[4]
Characteristics
η Sco A
Spectral type F5 IV[5]
U−B color index +0.09[2]
B−V color index +0.41[2]
Astrometry
η Sco A
Radial velocity (Rv)−27.0[6] km/s
Proper motion (μ) RA: +24.47[1] mas/yr
Dec.: −288.55[1] mas/yr
Parallax (π)44.39 ± 0.16[1] mas
Distance73.5 ± 0.3 ly
(22.53 ± 0.08 pc)
Absolute magnitude (MV)+1.58[7]
η Sco B
Radial velocity (Rv)−23.36±0.18[3] km/s
Proper motion (μ) RA: +24.01 mas/yr
Dec.: −288.55 mas/yr
Parallax (π)44.7788 ± 0.0324[3] mas
Distance72.84 ± 0.05 ly
(22.33 ± 0.02 pc)
Details
η Sco A
Mass1.60+0.01
−0.23[8] M☉
Radius3.307±0.050[9] R☉
Luminosity17.94±0.45[9] L☉
Surface gravity (log g)3.65±0.20[9] cgs
Temperature6,533±46[9] K
Metallicity [Fe/H]−0.29±0.10[9] dex
Rotational velocity (v sin i)150[9] km/s
Age1.1[7] Gyr
η Sco B
Mass0.527±0.017[10] M☉
Radius0.524±0.017[10] R☉
Luminosity0.050±0.001[10] L☉
Temperature3,643±121[10] K
Other designations
η Sco, CD−43 11485, FK5 638, GJ 657, HD 155203, HIP 84143, HR 6380, SAO 227707, WDS J17122-4314[11]
Database references
SIMBADEta Scorpii A
Eta Scorpii B

Eta Scorpii, Latinized from η Scorpii, is a binary star in the southern zodiac constellation of Scorpius. With an apparent visual magnitude of 3.33,[2] this is one of the brighter members of the Scorpius and is the furthest south of the constellation stars with a Bayer designation.[12] The distance to this system can be estimated using parallax measurements, yielding values of 73.48 ± 0.26 light-years (22.53 ± 0.08 parsecs) for the primary[1] and 72.84 ± 0.05 ly (22.333 ± 0.015 pc) for the secondary.[3]

Characteristics

The two components of this system are separated by 9.87" in the sky, and were identified as a gravitationally bound pair in 2018 with data from the Gaia spacecraft.[13]

The stellar classification of the primary star, Eta Scorpii A, has undergone some revision over time, with the star being classified anywhere from an F-type main sequence star to a giant star.[11] In 2006, the NStars program assigned it a class of F5 IV,[5] where the luminosity class of 'IV' indicates this is a subgiant star that is exhausting the supply of hydrogen at its core and is in the process of evolving into a giant star. It has around 1.6 times the Sun's mass[8] with an estimated age of 1.1 billion years.[7] The star is radiating about 18 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 6,533 K.[9] It is this heat that gives it a yellow-white hue that is typical for an F-type star.[14]

Eta Scorpii A is rotating rapidly, with a projected rotational velocity of 150 km s−1.[15] This is causing the star to spin on its axis with a period of less than a day.[16] It is an X-ray emitter with its stellar corona giving off an X-ray luminosity of 4.4×1028 ergs s−1.[17] In 1991 it was identified as a possible barium star, as it displays an enhanced abundance of the element barium in its spectrum.[18] Overall, the abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is similar to the abundance in the Sun.[7]

The secondary component, Eta Scorpii B, also designated L 413-148,[19] has a much fainter apparent magnitude of +11.23.[4] It has no published spectral type.[19] The star has roughly 0.53 times the mass of the Sun and 0.52 times the radius. It is radiating about 5% of the Sun's luminosity at an effective temperature of approximately 3,600 K.[10]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 Bok, B. J.; Bok, P. F.; Miller, E. W. (November 1972). "Photometric standards for the southern hemisphere. II". Astronomical Journal 77: 733. doi:10.1086/111346. Bibcode: 1972AJ.....77..733B. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  4. ↑ 4.0 4.1 Zacharias, N.; Finch, C. T.; Girard, T. M.; Henden, A.; Bartlett, J. L.; Monet, D. G.; Zacharias, M. I. (February 2013). "The Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)" (in en). The Astronomical Journal 145 (2): 44. doi:10.1088/0004-6256/145/2/44. ISSN 0004-6256. Bibcode: 2013AJ....145...44Z. 
  5. ↑ 5.0 5.1 Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Bubar, E. J.; McGahee, C. E.; O'Donoghue, A. A.; Knox, E. R. (July 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal 132 (1): 161–170. doi:10.1086/504637. Bibcode: 2006AJ....132..161G. 
  6. ↑ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". 30. University of Toronto: International Astronomical Union. p. 57. Bibcode: 1967IAUS...30...57E. 
  7. ↑ 7.0 7.1 7.2 7.3 Holmberg, J.; Nordstrom, B.; Andersen, J. (July 2009). "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics". Astronomy and Astrophysics 501 (3): 941–947. doi:10.1051/0004-6361/200811191. Bibcode: 2009A&A...501..941H. 
  8. ↑ 8.0 8.1 Vines, Jose I.; Jenkins, James S. (June 2022). "ARIADNE: measuring accurate and precise stellar parameters through SED fitting" (in en). Monthly Notices of the Royal Astronomical Society 513 (2): 2719–2731. doi:10.1093/mnras/stac956. ISSN 0035-8711. Bibcode: 2022MNRAS.513.2719V. 
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 Rains, Adam D.; Ireland, Michael J.; White, Timothy R.; Casagrande, Luca; Karovicova, I. (April 2020). "Precision angular diameters for 16 southern stars with VLTI/PIONIER". Monthly Notices of the Royal Astronomical Society 493 (2): 2377–2394. doi:10.1093/mnras/staa282. Bibcode: 2020MNRAS.493.2377R. 
  10. ↑ 10.0 10.1 10.2 10.3 10.4 Hardegree-Ullman, Kevin K.; Apai, Dániel; Bergsten, Galen J.; Pascucci, Ilaria; López-Morales, Mercedes (June 2023). "Bioverse: A Comprehensive Assessment of the Capabilities of Extremely Large Telescopes to Probe Earth-like O2 Levels in Nearby Transiting Habitable-zone Exoplanets" (in en). The Astronomical Journal 165 (6): 267. doi:10.3847/1538-3881/acd1ec. ISSN 0004-6256. Bibcode: 2023AJ....165..267H. 
  11. ↑ 11.0 11.1 "LTT 6848 -- High proper-motion Star". SIMBAD. Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Eta+Scorpii. 
  12. ↑ Burnham, Robert (1978). Burnham's celestial handbook: an observer's guide to the universe beyond the solar system. Dover books explaining science. 3 (2nd ed.). Courier Dover Publications. p. 1675. ISBN 0-486-23673-0. https://books.google.com/books?id=PJzIt3SIlkUC&pg=PA1675. 
  13. ↑ Fuhrmann, Klaus; Chini, Rolf (2018-06-01). "Nearby Gaia DR2 Companions". Research Notes of the AAS 2 (2): 56. doi:10.3847/2515-5172/aacc72. ISSN 2515-5172. Bibcode: 2018RNAAS...2...56F. 
  14. ↑ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. http://outreach.atnf.csiro.au/edu. 
  15. ↑ Mallik, Sushma V.; Parthasarathy, M.; Pati, A. K. (October 2003). "Lithium and rotation in F and G dwarfs and subgiants". Astronomy and Astrophysics 409 (1): 251–261. doi:10.1051/0004-6361:20031084. Bibcode: 2003A&A...409..251M. 
  16. ↑ Kaler, James B.. "Eta Scorpii". Stars. University of Illinois. http://stars.astro.illinois.edu/sow/etasco.html. 
  17. ↑ Pizzolato, N.; Maggio, A.; Sciortino, S. (September 2000). "Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases". Astronomy and Astrophysics 361: 614–628. Bibcode: 2000A&A...361..614P. 
  18. ↑ Lu, Phillip K. (June 1991). "Taxonomy of barium stars". Astronomical Journal 101: 2229–2254. doi:10.1086/115845. Bibcode: 1991AJ....101.2229L. 
  19. ↑ 19.0 19.1 "NLTT 44329". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NLTT+44329. 



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