Tau Octantis

τ Octantis
	Location of τ Octantis (circled)
Observation data; Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Octans
Right ascension	23h 28m 03.7855s
Declination	−87° 28′ 55.967″
Apparent magnitude (V)	5.50
Characteristics
Spectral type	K2 III
U−B color index	+1.43
B−V color index	+1.27
Astrometry
Radial velocity (Rv)	31.0±1.4 km/s
Proper motion (μ)	RA: +16.782 mas/yr ; Dec.: +11.957 mas/yr
Parallax (π)	6.8009±0.0574 mas
Distance	480 ± 4 ly ; (147 ± 1 pc)
Absolute magnitude (MV)	−0.36
Details
Mass	1.14 M☉
Radius	24 R☉
Luminosity	223 L☉
Surface gravity (log g)	1.63 cgs
Temperature	4,422 K
Metallicity [Fe/H]	+0.12 dex
Rotational velocity (v sin i)	<1 km/s
Other designations
	τ Oct, 81 G. Octantis, CPD−88°204, FK5 925, GC 32558, HD 219765, HIP 115836, HR 8862, SAO 258970
Database references
SIMBAD	data

Tau Octantis, Latinized from τ Octantis, is a solitary^[11] star in the southern circumpolar constellation Octans. It has an apparent magnitude of 5.50,^[2] allowing it to be faintly seen with the naked eye. The object is located at a distance of 480 light years^[1] but is receding with a heliocentric radial velocity of 31 km/s.^[5]

Tau Octantis has a stellar classification of K2 III, indicating that the object is a red giant. It has 114% the mass of the Sun^[6] but is 223 times as luminous.^[8] However, an enlarged radius of 24 R_☉ yields an effective temperature of 4,422 K,^[8] giving it an orange glow. Tau Octantis has an iron abundance 132% that of the Sun and is believed to be a member of the old disk population.^[9] Currently, it spins with a projected rotational velocity less than 1 km/s.^[10]

References

^ ^a ^b ^c ^d ^e 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.
^ ^a ^b ^c 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. ISSN 1063-7737. S2CID 255204555.
^ 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.
^ ^a ^b 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.
^ ^a ^b 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.
^ ^a ^b ^c Anders, F.; et al. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. ISSN 0004-6361.
^ Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. ISSN 0004-6256.
^ ^a ^b ^c ^d McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (21 November 2012). "Fundamental parameters and infrared excesses of Hipparcos stars: Parameters and IR excesses from Hipparcos". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–357. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. ISSN 0035-8711.
^ ^a ^b Eggen, O. J. (July 1993). "Evolved GK stars near the sun. I - The old disk population". The Astronomical Journal. 106: 80. Bibcode:1993AJ....106...80E. doi:10.1086/116622.
^ ^a ^b 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.
^ Eggleton, P. P.; Tokovinin, A. A. (3 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. S2CID 14878976.

[EDR3-1] 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.

[Anderson2012-2] 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. ISSN 1063-7737. S2CID 255204555.

[Houk1975-3] 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.

[Johnson1966-4] 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.

[Gontcharov2006-5] 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.

[Anders2019-6] Anders, F.; et al. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. ISSN 0004-6361.

[ticv8-7] Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. ISSN 0004-6256.

[McDonald2012-8] McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (21 November 2012). "Fundamental parameters and infrared excesses of Hipparcos stars: Parameters and IR excesses from Hipparcos". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–357. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. ISSN 0035-8711.

[Eggen1993-9] Eggen, O. J. (July 1993). "Evolved GK stars near the sun. I - The old disk population". The Astronomical Journal. 106: 80. Bibcode:1993AJ....106...80E. doi:10.1086/116622.

[DeMederios2014-10] 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.

[Eggelton2008-11] Eggleton, P. P.; Tokovinin, A. A. (3 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. S2CID 14878976.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

Observation data Epoch J2000.0 Equinox J2000.0 (ICRS)
Location of τ Octantis (circled)
Constellation	Octans
Right ascension	23^h 28^m 03.7855^s^[1]
Declination	−87° 28′ 55.967″^[1]
Apparent magnitude (V)	5.50^[2]
Characteristics
Spectral type	K2 III^[3]
U−B color index	+1.43^[4]
B−V color index	+1.27^[4]
Astrometry

Radial velocity (R_v)	31.0±1.4^[5] km/s
Proper motion (μ)	RA: +16.782 mas/yr^[1] Dec.: +11.957 mas/yr^[1]
Parallax (π)	6.8009±0.0574 mas^[1]
Distance	480 ± 4 ly (147 ± 1 pc)
Absolute magnitude (M_V)	−0.36^[2]

Details

Mass	1.14^[6] `M`_☉
Radius	24^[7] `R`_☉
Luminosity	223^[8] `L`_☉
Surface gravity (log g)	1.63^[6] cgs
Temperature	4,422^[8] K
Metallicity [Fe/H]	+0.12^[9] dex
Rotational velocity (v sin i)	<1^[10] km/s

Other designations
τ Oct, 81 G. Octantis, CPD−88°204, FK5 925, GC 32558, HD 219765, HIP 115836, HR 8862, SAO 258970
Database references
SIMBAD	data

Tau Octantis

Hub talks

Tau Octantis

Tau Octantis

Hub rules

Tau Octantis

Hub overview

Add your contribution

Inside this hub

Media Collections

Timelines

Articles

Notes collections

Notes

Days in Chronicle

Root Wikipedia Article

Tau Octantis

References

Add your contribution

Related Hubs