Iota Octantis

ι Octantis

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Octans
Right ascension	12^h 54^m 58.80949^s[1]
Declination	−85° 07′ 24.1041″[1]
Apparent magnitude (V)	5.83 + 6.75[2]
Characteristics
Spectral type	K0 III[3]
U−B color index	+0.79[4]
B−V color index	+1.02[4]
Astrometry
Radial velocity (Rv)	53.4±0.7[5] km/s
Proper motion (μ)	RA: +67.20[1] mas/yr Dec.: +24.76[1] mas/yr
Parallax (π)	9.27 ± 0.46 mas[1]
Distance	350 ± 20 ly (108 ± 5 pc)
Absolute magnitude (MV)	+0.29
Details[6]
Mass	2.49+1.48 −1.31 M☉
Radius	12.43[7] R☉
Luminosity	81±9 L☉
Temperature	4,890±110 K
Metallicity [Fe/H]	−0.3 dex
Rotational velocity (v sin i)	1.9±1.3[8] km/s
Age	725[9] Myr
Other designations
ι Octantis, 16 G. Octantis, CPD−84°407, GC 17460, HD 111482, HIP 63031, HR 4870, SAO 258654, WDS J12550-8507AB
Database references
SIMBAD	data

Iota Octantis, Latinized, from ι Octantis is a double star^[10] in the southern circumpolar constellation Octans. The "A" component has an apparent magnitude of 5.83,^[2] making it faintly visible to the naked eye under ideal conditions, but the "B" component can't be seen due to its faintness.^[2] The system is located at a distance of 350 light years^[1] based on its annual parallax shift, but is drifting away at a rate of 53.4 km/s.^[5]

Iota Octantis A has a classification of K0 III,^[3] which indicates that it is an evolved K-type star that exhausted hydrogen at its core and left the main sequence. It has an angular diameter of 1.07 arcseconds,^[11] which yields a radius 12.43 times that of the Sun at its estimated distance.^[7] At present Iota Octantis A has 2.49 times the mass of the Sun^[6] and radiates at 81 times the luminosity of the Sun^[6] from its enlarged photosphere at an effective temperature of 4,890 K,^[6] which gives it an orangish-yellow hue. Iota Octantis is metal deficient^[6] and spins slowly with a projected rotational velocity of 1.9 km/s.^[8]

Eggleton et al. states that both stars have similar spectral types,^[10] but there is a faint tenth magnitude companion with a classification of F8 located 60.1″ away,^[12] which is unrelated to the two.

References

1. van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy & Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. ISSN 0004-6361.
2. Fabricius, C.; Høg, E.; Makarov, V. V.; Mason, B. D.; Wycoff, G. L.; Urban, S. E. (March 2002). "The Tycho double star catalogue". Astronomy & Astrophysics. 384 (1): 180–189. Bibcode:2002A&A...384..180F. doi:10.1051/0004-6361:20011822. ISSN 0004-6361.
3. Houk, N.; Cowley, A. P. (1975). University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume I. Declinations -90_ to -53_ƒ0. Bibcode:1975mcts.book.....H.
4. Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (January 1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
5. Kharchenko, N.V.; Scholz, R.-D.; Piskunov, A.E.; Röser, S.; Schilbach, E. (November 2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889–896. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. ISSN 0004-6337.
6. Charbonnel, C.; Lagarde, N.; Jasniewicz, G.; North, P. L.; Shetrone, M.; Krugler Hollek, J.; Smith, V. V.; Smiljanic, R.; Palacios, A.; Ottoni, G. (January 2020). "Lithium in red giant stars: Constraining non-standard mixing with large surveys in the Gaia era". Astronomy & Astrophysics. 633: A34. arXiv:1910.12732. Bibcode:2020A&A...633A..34C. doi:10.1051/0004-6361/201936360. ISSN 0004-6361.
7. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:

   ${\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(108\cdot 1.07\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 24.86\cdot R_{\bigodot }\end{aligned}}}$

8. 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. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. ISSN 0004-6361.
9. "Digital Demo Room - Stellar Structure and Evolution Simulator". rainman.astro.illinois.edu. Retrieved 4 January 2022.
10. 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. ISSN 0035-8711.
11. Stevens, Daniel J.; Stassun, Keivan G.; Gaudi, B. Scott (29 November 2017). "Empirical Bolometric Fluxes and Angular Diameters of 1.6 Million Tycho-2 Stars and Radii of 350,000 Stars with Gaia DR1 Parallaxes". The Astronomical Journal. 154 (6): 259. arXiv:1708.05025. Bibcode:2017AJ....154..259S. doi:10.3847/1538-3881/aa957b. ISSN 0004-6256.
12. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (1 December 2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. ISSN 0004-6256.