Q Scorpii

Q Scorpii, also designated as HD 159433, is an astrometric binary[12] (100% chance)[13] located in the southern zodiac constellation Scorpius. It has an apparent magnitude of 4.27,[2] making it readily visible to the naked eye under ideal conditions. It lies in the tail of Scorpius, between the stars λ Scorpii and μ Scorpii and is located 7′ away from the faint globular cluster Tonantzintla 2. Based on parallax measurements from Gaia DR3, the system is estimated to be 158 light years distant,[1] but is approaching the Solar System with a heliocentric radial velocity of −49 km/s.[6]

Q Scorpii
Location of Q Scorpii on the map (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Scorpius
Right ascension 17h 36m 32.85514s[1]
Declination −38° 38′ 06.8918″[1]
Apparent magnitude (V) 4.27±0.01[2]
Characteristics
Evolutionary stage horizontal branch[3]
Spectral type K0 IIIb[4]
U−B color index +0.90[5]
B−V color index +1.08[5]
Astrometry
Radial velocity (Rv)−49±3[6] km/s
Proper motion (μ) RA: −16.762 mas/yr[1]
Dec.: −218.275 mas/yr[1]
Parallax (π)20.6922 ± 0.2161 mas[1]
Distance158 ± 2 ly
(48.3 ± 0.5 pc)
Absolute magnitude (MV)+0.67[7]
Details[8]
Mass1.10±0.07 M☉
Radius12.39±0.47 R☉
Luminosity62.2±4.2 L☉
Surface gravity (log g)2.41±0.11 cgs
Temperature4,605±40 K
Metallicity [Fe/H]−0.28±0.02 dex
Rotational velocity (v sin i)<1[9] km/s
Other designations
Q Scorpii, 159 G. Scorpii[10], CD−38°12044, CPD−38°6933, GC 23846, HD 159433, HIP 86170, HR 6546, SAO 209019[11]
Database references
SIMBADdata

The visible component is a red giant with a stellar classification of K0 IIIb.[4] The IIIb luminosity class indicates that it is a lower luminosity giant star. Q Scorpii is a red clump star located on the cool end of the horizontal branch,[3] fusing helium at its core. It has 110% the mass of the Sun but has expanded to 12.4 times its girth.[8] It radiates 62 times the luminosity of the Sun from its photosphere at an effective temperature of 4,605 K,[8] giving it an orange hue. Q Scorpii has an iron abundance half of the Sun's, making it metal deficient.[8] Like most giant stars, it spins slowly, having a projected rotational velocity lower than 1 km/s.[9]

References
  1. 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.
  2. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
  3. Laney, C. D.; Joner, M. D.; Pietrzyński, G. (11 November 2011). "A new Large Magellanic Cloud K-band distance from precision measurements of nearby red clump stars". Monthly Notices of the Royal Astronomical Society. 419 (2): 1637–1641. arXiv:1109.4800. Bibcode:2012MNRAS.419.1637L. doi:10.1111/j.1365-2966.2011.19826.x. ISSN 0035-8711.
  4. Hoffleit, Dorrit; Shapley, Harlow (1937). "Spectroscopic absolute magnitudes of three hundred and seventy southern stars". Annals of Harvard College Observatory. 105 (3): 45–68. Bibcode:1937AnHar.105...45H.
  5. Cousins, A. W. J. (1971). "Photometric standard stars". Royal Observatory Annals. 7. Bibcode:1971ROAn....7.....C.
  6. Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
  7. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
  8. Ottoni, G.; Udry, S.; Ségransan, D.; Buldgen, G.; Lovis, C.; Eggenberger, P.; Pezzotti, C.; Adibekyan, V.; Marmier, M.; Mayor, M.; Santos, N. C.; Sousa, S. G.; Lagarde, N.; Charbonnel, C. (January 2022). "CORALIE radial-velocity search for companions around evolved stars (CASCADES): I. Sample definition and first results: Three new planets orbiting giant stars". Astronomy & Astrophysics. 657: A87. arXiv:2201.01528. Bibcode:2022A&A...657A..87O. doi:10.1051/0004-6361/202040078. eISSN 1432-0746. ISSN 0004-6361.
  9. De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. eISSN 1432-0746. ISSN 0004-6361.
  10. Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
  11. "Q Scorpii". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 18, 2022.
  12. Eggleton, P. P.; Tokovinin, A. A. (11 September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. eISSN 1365-2966. ISSN 0035-8711.
  13. Frankowski, A.; Jancart, S.; Jorissen, A. (19 December 2006). "Proper-motion binaries in the Hipparcos catalogue". Astronomy & Astrophysics. 464 (1): 377–392. arXiv:astro-ph/0612449. Bibcode:2007A&A...464..377F. doi:10.1051/0004-6361:20065526. eISSN 1432-0746. ISSN 0004-6361.
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