RS Sagittarii

A visual band light curve for RS Sagittarii, adapted from Shobbrook (2005)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 17m 36.246s[2]
Declination −34° 06′ 26.16″[2]
Apparent magnitude (V) max: 6.01
min1: 6.97
min2: 6.28[3]
Characteristics
Evolutionary stage Main sequence
Spectral type B5V + A2V[4][5]
B−V color index −0.096±0.012[6]
Variable type Semidetached Algol[3]
Astrometry
Radial velocity (Rv)10.1±4.3[7] km/s
Proper motion (μ) RA: −2.946 mas/yr[2]
Dec.: −10.190 mas/yr[2]
Parallax (π)2.2918 ± 0.0977 mas[2]
Distance1,420 ± 60 ly
(440 ± 20 pc)
Absolute magnitude (MV)−1.58[6]
Orbit[8]
Period (P)2.4156848 d
Semi-major axis (a)16.09 R☉[5]
Eccentricity (e)0.0
Periastron epoch (T)2,453,971.1436±0.0038 HJD
Semi-amplitude (K1)
(primary)		88.3±1.6 km/s
Semi-amplitude (K2)
(secondary)		271.7±1.6 km/s
Details
Primary
Mass7.18[8] M☉
Radius5.11[8] R☉
Luminosity1,350[5] L☉
Temperature15,480[5] K
Secondary
Mass2.41[8] M☉
Radius4.10[8] R☉
Luminosity89.1[5] L☉
Temperature8,760[5] K
Other designations
RS Sgr, CD−34°12673, GC 24947, HD 167647, HIP 89637, HR 6833, SAO 209959, WDS J18176-3406A[9]
Database references
SIMBADdata

RS Sagittarii is an eclipsing binary star system in the southern constellation of Sagittarius, abbreviated RS Sgr. It is a double-lined spectroscopic binary with an orbital period of 2.416 days,[8] indicating that the components are too close to each other to be individually resolved. The system has a combined apparent visual magnitude of 6.01, which is bright enough to be faintly visible to the naked eye. During the primary eclipse the brightness drops to magnitude 6.97, while the secondary eclipse is of magnitude 6.28.[3] The distance to this system is approximately 1,420 light years based on parallax measurements.[2]

The variability of this system was initially suspected by B. A. Gould in 1879, then confirmed by A. W. Roberts in 1895. Roberts determined this to be an Algol-type variable with a period of 2.416 days.[10] In his 1915 study of eclipsing binaries, H. Shapley listed a low orbital eccentricity of 0.091 for this binary system. He considered both eclipses to be partial, but only after correcting for limb darkening.[11] R. S. Dugan and F. W. Wright in 1939 discovered evidence that suggested the period is varying.[12]

R. L. Baglow in 1948 found an essentially circular orbit with a primary component of spectral class B5.[13] By 1986, O. E. Ferrer and J. Sahade were able to extract spectral information about the secondary component, finding the system consists of ordinary main sequence stars of classes B5V and A2V. Hydrogen alpha emission lines suggested that the stars are interacting.[4] The system appears to be semidetached,[8] and may have already undergone a mass exchange phase.[14]

The primary component of the system is the more massive of the pair, having 7.18 times the mass of the Sun compared to 2.41 times the Sun's mass for the secondary member. The primary is the larger star, with 5.11 times the Sun's radius while the secondary has 2.41 solar radii.[5] The pair are separated by about 16 times the radius of the Sun.[8] The primary is radiating 1,350 times the Sun's luminosity from its photosphere at an effective temperature of 15,480 K. The cooler secondary is 8,760 K and radiates 89.1 times the luminosity of the Sun.[5]

RS Sgr shares a common proper motion with the 9th-magnitude stars TYC-7400-1102-1[15] and HD 167669,[16] and they would form a quadruple system. Any orbits would take hundreds of thousands of years. TYC-7400-1102-1 is an A1 main-sequence star with a mass around twice that of the Sun, while HD 167669 is a slightly brighter B9 main sequence star with a mass about three times the Sun's.[17] HD 167669 itself has a close optical companion, but it appears to be much more distant.[18] Together with RS Sgr, these stars have the Washington Double Star Catalog designation WDS J18176-3406.[19]

References

  1. ↑ Shobbrook, R. R. (December 2005). "Photometry of 20 eclipsing and ellipsoidal binary systems". The Journal of Astronomical Data. 11. Retrieved 7 December 2022.
  2. 1 2 3 4 5 6 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. 1 2 3 Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  4. 1 2 Ferrer, Osvaldo E.; Sahade, Jorge (December 1986), "Lines of the fainter component in the spectrum of RS Sagittarii", Publications of the Astronomical Society of the Pacific, 98: 1342–1346, Bibcode:1986PASP...98.1342F, doi:10.1086/131941, S2CID 122286399.
  5. 1 2 3 4 5 6 7 8 Malkov, Oleg Yu (February 2020), "Semidetached double-lined eclipsing binaries: Stellar parameters and rare classes", Monthly Notices of the Royal Astronomical Society, 491 (4): 5489–5497, Bibcode:2020MNRAS.491.5489M, doi:10.1093/mnras/stz3363.
  6. 1 2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  7. ↑ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  8. 1 2 3 4 5 6 7 8 Bakış, V.; et al. (January 2010), "The spectroscopic orbits of three double-lined eclipsing binaries: I. BG Ind, IM Mon, RS Sgr", New Astronomy, 15 (1): 1–7, arXiv:0905.0457, Bibcode:2010NewA...15....1B, doi:10.1016/j.newast.2009.05.005, S2CID 16670182.
  9. ↑ "RS Sgr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2022-12-03.
  10. ↑ Roberts, Alexander W. (July 1895), "Observations of southern variable stars", Astronomical Journal, 15 (349): 100–101, Bibcode:1895AJ.....15..100R, doi:10.1086/102250.
  11. ↑ Shapley, Harlow (1915), "A Study of the Orbits of Eclipsing Binaries", Contributions from the Princeton University Observatory, 3: iii–176, Bibcode:1915CoPri...3....1S. See pp. 66–67, 84.
  12. ↑ Sahade, Jorge (January 1949), "Spectrographic Observations of the Eclipsing Variable RS Sagittarii", Astrophysical Journal, 109: 116, Bibcode:1949ApJ...109..116S, doi:10.1086/145111.
  13. ↑ Baglow, R. L. (1948), "The Photometric Elements of RS Sagittarii", Monthly Notices of the Royal Astronomical Society, 108 (4): 343, Bibcode:1948MNRAS.108..343B, doi:10.1093/mnras/108.4.343.
  14. ↑ Cerruti, Miguel Angel; de Laurenti, Miguel Angel (1990), "The system of RS Sagittarii", Acta Astronomica, 40: 283, Bibcode:1990AcA....40..283C.
  15. ↑ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  16. ↑ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  17. ↑ Tokovinin, Andrei (March 1, 2018), "The Updated Multiple Star Catalog", The Astrophysical Journal Supplement Series, 235 (1): 6, arXiv:1712.04750, Bibcode:2018ApJS..235....6T, doi:10.3847/1538-4365/aaa1a5, ISSN 0067-0049, S2CID 119047709.
  18. ↑ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  19. ↑ Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2016-09-04.
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