Astronomy:18 Sextantis

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Short description: K-type giant star in the constellation Sextans
18 Sextantis
Sextans constellation map.svg
Red circle.svg
Location of 18 Sex on the map (circled)
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Sextans
Right ascension  10h 10m 55.86074s[1]
Declination −08° 25′ 06.4527″[1]
Apparent magnitude (V) 5.62±0.01[2]
Characteristics
Spectral type K2/3 III[3]
U−B color index +1.42[4]
B−V color index +1.30[4]
Astrometry
Radial velocity (Rv)0.2±2.9[5] km/s
Proper motion (μ) RA: −0.115[1] mas/yr
Dec.: −43.987[1] mas/yr
Parallax (π)5.8416 ± 0.0881[1] mas
Distance558 ± 8 ly
(171 ± 3 pc)
Absolute magnitude (MV)−0.16[6]
Details
Radius27.3±1.4[7] R☉
Luminosity222±12[8] L☉
Surface gravity (log g)1.72[9] cgs
Temperature4,410±122[10] K
Metallicity [Fe/H]−0.31+0.01−0.00[11] dex
Rotational velocity (v sin i)<1.0[12] km/s
Other designations
18 Sex, BD−07°2977, GC 13990, HD 88333, HIP 49865, HR 3996, SAO 137395[13]
Database references
SIMBADdata

18 Sextantis (HD 88333; HR 3996; 32 G. Sextantis), or simply 18 Sex, is a solitary star[14] located in the southern constellation Sextans. It is faintly visible to the naked eye as an orange-hued point of light with an apparent magnitude of 5.62.[2] Gaia DR3 parallax measurements imply a distance of 558 light-years[1] and it is slowly receding with a poorly constrained heliocentric radial velocity of approximately 0.2 km/s.[5] At its current distance, 18 Sex's brightness is diminished with an interstellar extinction of two-tenths of a magnitude[15] and it has an absolute magnitude of −0.16.[6]

18 Sex has a stellar classification of K2/3 III,[3] indicating that it is an evolved star with the characteristics of a K2 and K3 giant star. At present, it has exhausted hydrogen at its core and it has expanded to 27.3 times the radius of the Sun.[7] It radiates 222 times the luminosity of the Sun[8] from its enlarged photosphere at an effective temperature of 4,410 K.[10] Gaia DR3 models it to be a larger and brighter red giant branch star with a radius of 35.27 R☉ and a luminosity of 384 L☉.[1] 18 Sex is metal deficient with an iron abundance of [Fe/H] = −0.31 or 49% of the Sun's[11] and it spins too slowly for its projected rotational velocity to be measured accurately, having a velocity lower than 1.0 km/s.[12]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 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.
  2. ↑ 2.0 2.1 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H. 
  3. ↑ 3.0 3.1 Houk, Nancy; Swift, Carrie (1999). Michigan catalogue of two-dimensional spectral types for the HD Stars ; vol. 5. Bibcode: 1999mctd.book.....H. 
  4. ↑ 4.0 4.1 Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory 4: 99–110. Bibcode: 1966CoLPL...4...99J. 
  5. ↑ 5.0 5.1 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. doi:10.1134/S1063773706110065. ISSN 1063-7737. Bibcode: 2006AstL...32..759G. 
  6. ↑ 6.0 6.1 Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode: 2012AstL...38..331A. 
  7. ↑ 7.0 7.1 Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (April 8, 2004). "The angular sizes of dwarf stars and subgiants: Surface brightness relations calibrated by interferometry". Astronomy & Astrophysics 426 (1): 297–307. doi:10.1051/0004-6361:20035930. ISSN 0004-6361. Bibcode: 2004A&A...426..297K. 
  8. ↑ 8.0 8.1 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.
  9. ↑ McDonald, I.; Zijlstra, A. A.; Watson, R. A. (15 June 2017). "Fundamental parameters and infrared excesses of Tycho–Gaia stars". Monthly Notices of the Royal Astronomical Society 471 (1): 770–791. doi:10.1093/mnras/stx1433. ISSN 0035-8711. Bibcode: 2017MNRAS.471..770M. 
  10. ↑ 10.0 10.1 Stassun, Keivan G. et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal 158 (4): 138. doi:10.3847/1538-3881/ab3467. Bibcode: 2019AJ....158..138S. 
  11. ↑ 11.0 11.1 Poggio, E.; Recio-Blanco, A.; Palicio, P. A.; Re Fiorentin, P.; de Laverny, P.; Drimmel, R.; Kordopatis, G.; Lattanzi, M. G. et al. (30 September 2022). "The chemical signature of the Galactic spiral arms revealed by Gaia DR3". Astronomy & Astrophysics 666: L4. doi:10.1051/0004-6361/202244361. ISSN 0004-6361. Bibcode: 2022A&A...666L...4P. 
  12. ↑ 12.0 12.1 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 V: Southern stars *". Astronomy & Astrophysics 561: A126. doi:10.1051/0004-6361/201220762. ISSN 0004-6361. Bibcode: 2014A&A...561A.126D. 
  13. ↑ "* 18 Sex". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+18+Sex. 
  14. ↑ 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. doi:10.1111/j.1365-2966.2008.13596.x. ISSN 0035-8711. Bibcode: 2008MNRAS.389..869E. 
  15. ↑ Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society 472 (4): 3805–3820. doi:10.1093/mnras/stx2219. ISSN 0035-8711. Bibcode: 2017MNRAS.472.3805G. 
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