9 Equulei

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9 Equulei
Observation data
Epoch J2000       Equinox J2000
Constellation Equuleus
Right ascension 21h 21m 04.825s [1]
Declination +07° 21′ 16.21″ [1]
Apparent magnitude  (V)5.798 [2]
Characteristics
Evolutionary stage AGB [3]
Spectral type M2IIIa [4]
U−B color index +1.97 [5]
B−V color index +1.66 [5]
Variable type suspected [6]
Astrometry
Radial velocity (Rv)−21.82±0.30 [1] km/s
Proper motion (μ)RA: 43.871±0.274 [1] mas/yr
Dec.: −17.822±0.261 [1] mas/yr
Parallax (π)4.3895±0.1647  mas [1]
Distance 740 ± 30  ly
(228 ± 9  pc)
Absolute magnitude  (MV)−0.69 [7]
Details
Mass 1.2 [8]   M☉
Radius 58 [1]   R☉
Luminosity 720 [1]   L☉
Surface gravity (log g)1.64 [8]   cgs
Temperature 3,920 [1]   K
Metallicity [Fe/H]−0.27 [8]   dex
Other designations
HIP  105413, HD  203291, HR  8163, SAO  126719
Database references
SIMBAD data

9 Equulei is an M-type star in the constellation Equuleus. It is an asymptotic giant branch (AGB) star, a star that has exhausted its core helium and is now fusing both hydrogen and helium in shells outside the core. [3] It is also a suspected variable star with an amplitude of about 0.05 magnitudes. [6]

The spectral type is M2IIIa, meaning it is a relatively cool giant star. As an AGB star, it is burning hydrogen and helium in shells around an inert carbon-oxygen core. It has expanded to 58 times the radius of the Sun, and it radiates 720 times as much electromagnetic radiation from a photosphere with an effective temperature of 3,920  K .

References

  1. 1 2 3 4 5 6 7 8 9 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 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. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H.
  3. 1 2 Eggen, Olin J. (1992). "Asymptotic Giant Branch Stars Near the Sun". The Astronomical Journal. 104: 275. Bibcode:1992AJ....104..275E. doi:10.1086/116239.
  4. ↑ Yamashita, Y. (1967). "MK Spectral Types of Bright M-Type Stars". Publications of the Dominion Astrophysical Observatory Victoria. 13: 47. Bibcode:1967PDAO...13...47Y.
  5. 1 2 Hoffleit, Dorrit; Jaschek, Carlos (1991). "The Bright star catalogue". New Haven, Conn.: Yale University Observatory, 5th Rev.ed. Bibcode:1991bsc..book.....H.
  6. 1 2 Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
  7. ↑ 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.
  8. 1 2 3 Khalatyan, A.; Anders, F.; Chiappini, C.; Queiroz, A. B. A.; Nepal, S.; Dal Ponte, M.; Jordi, C.; Guiglion, G.; Valentini, M.; Torralba Elipe, G.; Steinmetz, M.; Pantaleoni-González, M.; Malhotra, S.; Jiménez-Arranz, Ó.; Enke, H.; Casamiquela, L.; Ardèvol, J. (2024). "Transferring spectroscopic stellar labels to 217 million Gaia DR3 XP stars with SHBoost". Astronomy and Astrophysics. 691: A98. arXiv: 2407.06963 . Bibcode:2024A&A...691A..98K. doi:10.1051/0004-6361/202451427.
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