GCIRS 16SW

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GCIRS 16SW
GCIRS16SWLocation.png
The location of GCIRS 16SW (circled in red)
Observation data
Epoch J2000       Equinox J2000
Constellation Sagittarius [1]
Right ascension 17h 45m 40.124s [2]
Declination −29° 00′ 29.02″ [2]
Characteristics
Evolutionary stage Slash star
Spectral type Ofpe/WN9 [3]
Apparent magnitude  (J)14.75 [4]
Apparent magnitude  (H)11.6 [4]
Apparent magnitude  (K)9.34 [5]
Orbit [6]
Primary Sagittarius A*
CompanionGCIRS 16SW
Period (P)1270±309  yr
Semi-major axis (a)2.32±0.46″
Eccentricity (e)0.35±0.11
Inclination (i)113.0±1.3°
Longitude of the node (Ω)113.2±1.4°
Periastron epoch (T)2132±29
Argument of periastron (ω)
(secondary)		28±14°
Orbit [7]
Period (P)19.4513±0.0011  d
Semi-major axis (a)140.6±4.7  R☉
Inclination (i)70.85±0.6°
Periastron epoch (T)2451775.102±0.032
Details [7]
A
Mass ~50  M☉
Radius 54.5±1.8 × 58.2±1.9 × 62.7±2.1  R☉
Luminosity 1,100,000  L☉
Surface gravity (log g)3.0  cgs
Temperature 24,400  K
B
Mass ~50  M☉
Radius 54.5±1.8 × 58.2±1.9 × 62.7±2.1  R☉
Luminosity1,100,000  L☉
Surface gravity (log g)3.0  cgs
Temperature 23,500  K
Other designations
GCIRS 16SW, S97, S1-16 [8]
Database references
SIMBAD data

GCIRS 16SW, also known as S97, is a contact binary star located in the Galactic Center. It is composed of two hot massive stars of equal size that orbit each other with a period of 19.5 days. The stars are so close that their atmospheres overlap, and the two stars form an eclipsing binary varying in brightness by 0.35 magnitudes at infrared wavelengths. [7]

Artist's impression of GCIRS 16SW GCIRS 16SW Celestia.png
Artist's impression of GCIRS 16SW

GCIRS 16SW orbits Sagittarius A* at approximately 19,000 AU, with a period of approximately 1,270 years. [6] At the stars' estimated mass of about 50 solar masses, they are predicted to have a lifespan of about 4 million years, indicating that the system formed within 0.1 parsecs (0.33  ly ; 21,000  AU ) of Sagittarius A*, instead of having migrated inward from a greater distance. [7]

GCIRS 16SW was classified as a candidate luminous blue variable on the basis of its spectrum and physical properties. [9] This was before it was identified as an eclipsing binary, but it is still treated as a candidate LBV. [10]

Each star is strongly distorted by the gravity of the other star. The polar radius is calculated to be 54.5  R☉, while the radius along the direction of orbital motion is 58.2 R☉. The radius along the line joining the two stars is 62.7 R☉, while the separation of the centres of the two stars is 132.8 R☉. A calculation of properties treating the binary as a single star gave an effective temperature of 24,400  K . [9] The secondary component is found to have a temperature 96% of that of the primary. However, these temperatures yield a luminosity over a million times that of the sun, uncomfortably close to the Eddington luminosity for each star, and it is suspected the actual temperatures are slightly lower. [7]

References

  1. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific . 99 (617): 695. Bibcode:1987PASP...99..695R. doi: 10.1086/132034 . Constellation record for this object at VizieR.
  2. 1 2 Miho N. Ishigaki; Nozomu Tominaga; Chiaki Kobayashi; Ken'ichi Nomoto (2014). "Faint Population III Supernovae as the Origin of the Most Iron-Poor Stars". The Astrophysical Journal Letters. 792 (2): L32. arXiv: 1404.4817 . Bibcode:2014ApJ...792L..32I. doi:10.1088/2041-8205/792/2/L32. S2CID   119012372.
  3. ↑ Paumard, T.; Genzel, R.; Martins, F.; Nayakshin, S.; Beloborodov, A.M.; Levin, Y.; Trippe, S.; Eisenhauer, F.; Ott, T.; Gillessen, S.; Abuter, R.; Cuadra, J.; Alexander, T.; Sternberg, A. (2006). "The two young star disks in the central parsec of the galaxy: Properties, dynamics, and formation". The Astrophysical Journal. 643 (2): 1011–1035. arXiv: astro-ph/0601268 . Bibcode:2006ApJ...643.1011P. doi:10.1086/503273. S2CID   14440768.
  4. 1 2 Blum, R. D.; Ramírez, Solange V.; Sellgren, K.; Olsen, K. (2003). "Really Cool Stars and the Star Formation History at the Galactic Center". The Astrophysical Journal. 597 (1): 323–346. arXiv: astro-ph/0307291 . Bibcode:2003ApJ...597..323B. doi:10.1086/378380. S2CID   5664467.
  5. ↑ Blum, R. D.; Sellgren, K.; Depoy, D. L. (1996). "JHKL Photometry and the K-Band Luminosity Function at the Galactic Center". The Astrophysical Journal. 470: 864. arXiv: astro-ph/9604109 . Bibcode:1996ApJ...470..864B. doi:10.1086/177917. S2CID   2730271.
  6. 1 2 Gillessen, S.; Plewa, P. M.; Eisenhauer, F.; Sari, R.; Waisberg, I.; Habibi, M.; Pfuhl, O.; George, E.; Dexter, J. (2017). "An Update on Monitoring Stellar Orbits in the Galactic Center". The Astrophysical Journal. 837 (1): 30. arXiv: 1611.09144 . Bibcode:2017ApJ...837...30G. doi: 10.3847/1538-4357/aa5c41 . ISSN   0004-637X. S2CID   119087402.
  7. 1 2 3 4 5 Peeples, Molly S.; et al. (January 2007). "The Nature of the Variable Galactic Center Source GCIRS 16SW Revisited: A Massive Eclipsing Binary". The Astrophysical Journal . 654 (1): L61 –L64. arXiv: astro-ph/0610212 . Bibcode:2007ApJ...654L..61P. doi:10.1086/510720. S2CID   14242573.
  8. ↑ "GCIRS 16SW -- Wolf-Rayet Star". SIMBAD. Centre de Données astronomiques de Strasbourg . Retrieved 30 June 2020.
  9. 1 2 Najarro, F.; Krabbe, A.; Genzel, R.; Lutz, D.; Kudritzki, R. P.; Hillier, D. J. (1997). "Quantitative spectroscopy of the HeI cluster in the Galactic center". Astronomy and Astrophysics. 325: 700. Bibcode:1997A&A...325..700N.
  10. ↑ Smith, Nathan; Aghakhanloo, Mojgan; Murphy, Jeremiah W.; Drout, Maria R.; Stassun, Keivan G.; Groh, Jose H. (2019). "On the Gaia DR2 distances for Galactic luminous blue variables". Monthly Notices of the Royal Astronomical Society. 488 (2): 1760. arXiv: 1805.03298 . Bibcode:2019MNRAS.488.1760S. doi: 10.1093/mnras/stz1712 . S2CID   119267371.
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