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36 Ophiuchi
	36 Location of 36 Ophiuchi in the constellation Ophiuchus;
Observation data; Epoch J2000 Equinox J2000
Constellation	Ophiuchus
Right ascension	A: 17h 15m 20.851s; B: 17h 15m 20.978s; C: 17h 16m 13.3624s
Declination	A: −26° 36′ 09.04″; B: −26° 36′ 10.18″; C: −26° 32′ 46.129″
Apparent magnitude (V)	5.08/5.03/6.34
Characteristics
Spectral type	K2 V/K1 V/K5 V
U−B color index	0.51(AB)/1.04
B−V color index	0.85(AB)/1.16
Variable type	C: RS CVn
Astrometry
36 Oph A
Radial velocity (Rv)	−0.6 km/s
Proper motion (μ)	RA: −498.600 mas/yr ; Dec.: −1,149.158 mas/yr
Parallax (π)	168.0031 ± 0.1343 mas
Distance	19.41 ± 0.02 ly ; (5.952 ± 0.005 pc)
36 Oph B
Radial velocity (Rv)	0.0 km/s
Proper motion (μ)	RA: −465.861 mas/yr ; Dec.: −1,141.168 mas/yr
Parallax (π)	168.1303 ± 0.1081 mas
Distance	19.40 ± 0.01 ly ; (5.948 ± 0.004 pc)
36 Oph C
Radial velocity (Rv)	−0.04±0.22 km/s
Proper motion (μ)	RA: −479.573 mas/yr ; Dec.: −1,124.332 mas/yr
Parallax (π)	167.9617 ± 0.0311 mas
Distance	19.418 ± 0.004 ly ; (5.954 ± 0.001 pc)
Orbit
Companion	36 Ophiuchi B
Period (P)	470.9 yr
Semi-major axis (a)	13″
Eccentricity (e)	0.916
Inclination (i)	99.8°
Details
36 Oph A
Mass	0.75+0.02; −0.04 M☉
Radius	0.817±0.016 R☉
Luminosity	0.326±0.084 L☉
Temperature	5,103±29 K
Metallicity [Fe/H]	−0.23 dex
Age	4.86+0.50; −0.22 Gyr
36 Oph B
Mass	0.76+0.03; −0.06 M☉
Radius	0.709 R☉
Luminosity	0.32 L☉
Surface gravity (log g)	4.61 cgs
Temperature	5,171±71 K
Metallicity [Fe/H]	−0.22 dex
Age	5.26+5.04; −2.94 Gyr
Other designations
	36 Oph, WDS J17153-2636
	AB: GJ 663, CD−26°12026, GCTP 3908.00, HIP 84405
	A: Guniibuu, HR 6402, HD 155886, LHS 437, SAO 185198
	B: HR 6401, HD 155885, LHS 438, SAO 185199
	C: V2215 Ophiuchi, GJ 664, CD−26°12036, HD 156026, GCTP 3913.00, LHS 439, SAO 185213, HIP 84478
Database references
SIMBAD	AB
	A
	B
	C
Exoplanet Archive	A
	B
	C
ARICNS	A
	B
	C

36 Ophiuchi (or Guniibuu for component A) is a triple star system 19.5 light-years from Earth in the constellation Ophiuchus.

Characteristics

The primary and secondary stars (also known as HD 155886) are nearly identical orange main-sequence dwarfs of spectral type K2/K1. This binary is unusual because its eruptions do not seem to conform to the Waldmeier effect; that is, the strongest eruptions of HD 155886 are not the ones characterized by the fast eruption onset.^[10] The tertiary star is an orange main-sequence dwarf of spectral type K5.

A visual band light curve for 36 Ophiuchi C (V2215 Ophiuchi), plotted from *ASAS-SN* data^[11]

Star C is separated from the A-B pair by 700 arcseconds, compared to a minimum of 4.6 arcseconds for A-B, so its effect on the movements of the A-B pair is small. A and B have active chromospheres. At present the distance between the stars forming the AB-pair is 5.1 arcseconds and the position angle is 139 degrees, while star C is 731.6 arcseconds away from the A-component and situated at a position angle of 74 degrees.

Nomenclature

In the beliefs of the Kamilaroi and Euahlayi Aboriginal peoples in New South Wales, Australia, the star is called Guniibuu that represents the robin red-breast bird (Petroica boodang). In 2016, the IAU organized a Working Group on Star Names (WGSN)^[12] to catalog and standardize proper names for stars. The WGSN approved the name Guniibuu for the star A on 10 August 2018 and it is now so included in the List of IAU-approved Star Names.^[13]

Hunt for substellar objects

The McDonald Observatory team has set limits to the presence of one or more planets^[14] around 36 Ophiuchi A with masses between 0.13 and 5.4 Jupiter masses and average separations spanning between 0.05 and 5.2 astronomical units (AU), although beyond 1.5 AU orbits are inherently unstable around either 36 Ophiuchi A or 36 Ophiuchi B.^[15]

The star C (or namely HD 156026) is among five nearby paradigms as K-type stars of a type in a 'sweet spot’ between Sun-analog stars and M stars for the likelihood of evolved life, per analysis of Giada Arney from NASA's Goddard Space Flight Center.^[16]

Notes

^ Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K: ${\sqrt {{\biggl (}{\frac {5,772}{5,171}}{\biggr )}^{4}\cdot 10^{-0.49}}}=0.709\ R_{\odot }.$

References

^ ^a ^b ^c ^d ^e ^f
"SIMBAD Astronomical Database". Centre de Données astronomiques de Strasbourg. Retrieved 2013-08-23.
^ ^a ^b 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 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 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.
^ Tokovinin, Andrei (July 2017). "Orbit Alignment in Triple Stars". The Astrophysical Journal. 844 (2): 103. arXiv:1706.00748. Bibcode:2017ApJ...844..103T. doi:10.3847/1538-4357/aa7746. ISSN 0004-637X.
^ ^a ^b ^c ^d Luck, R. Earle (2017-01-01). "Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants". The Astronomical Journal. 153 (1): 21. arXiv:1611.02897. Bibcode:2017AJ....153...21L. doi:10.3847/1538-3881/153/1/21. ISSN 0004-6256.36 Ophiuchi A's database entry at VizieR.
^ Demory, Brice-Olivier; Ségransan, Damien; Forveille, Thierry; Queloz, Didier; Beuzit, Jean-Luc; Delfosse, Xavier; Di Folco, Emmanuel; Kervella, Pierre; Le Bouquin, Jean-Baptiste; Perrier, Christian; Benisty, Myriam; Duvert, Gilles; Hofmann, Karl-Heinz; Lopez, Bruno; Petrov, Romain (October 2009). "Mass-radius relation of low and very low-mass stars revisited with the VLTI". Astronomy and Astrophysics. 505 (1): 205–215. arXiv:0906.0602. Bibcode:2009A&A...505..205D. doi:10.1051/0004-6361/200911976. S2CID 14786643.
^ Hardegree-Ullman, Kevin K.; Apai, Dániel; Bergsten, Galen J.; Pascucci, Ilaria; López-Morales, Mercedes (2023-06-01). "Bioverse: A Comprehensive Assessment of the Capabilities of Extremely Large Telescopes to Probe Earth-like O2 Levels in Nearby Transiting Habitable-zone Exoplanets". The Astronomical Journal. 165 (6): 267. arXiv:2304.12490. Bibcode:2023AJ....165..267H. doi:10.3847/1538-3881/acd1ec. ISSN 0004-6256. 36 Ophiuchi A's database entry at VizieR.
^ ^a ^b ^c ^d ^e ^f ^g Luck, R. Earle (2018-03-01). "Abundances in the Local Region. III. Southern F, G, and K Dwarfs". The Astronomical Journal. 155 (3): 111. Bibcode:2018AJ....155..111L. doi:10.3847/1538-3881/aaa9b5. ISSN 0004-6256. 36 Ophiuchi B's database entry at VizieR.
^ Garg, Suyog; Karak, Bidya Binay; Egeland, Ricky; Soon, Willie; Baliunas, Sallie (2019), "Waldmeier Effect in Stellar Cycles", The Astrophysical Journal, 886 (2): 132, arXiv:1909.12148, Bibcode:2019ApJ...886..132G, doi:10.3847/1538-4357/ab4a17, S2CID 202888617
^ "ASAS-SN Variable Stars Database". ASAS-SN Variable Stars Database. ASAS-SN. Retrieved 6 January 2022.
^ "IAU Working Group on Star Names (WGSN)". Retrieved 17 September 2018.
^ "IAU Catalog of Star Names". International Astronomical Union. Retrieved 2018-09-17.
^ Wittenmeyer et al. (2006).
^ Irwin et al. (1996).
^ Bill Steigerwald (2019-03-07). ""Goldilocks" Stars May Be "Just Right" for Finding Habitable Worlds". NASA. Retrieved 2020-05-12. 'I find that certain nearby K stars like 61 Cyg A/B, Epsilon Indi, Groombridge 1618, and HD 156026 may be particularly good targets for future biosignature searches,' said Arney.

External links

"36 Ophiuchi". SolStation. Retrieved 3 November 2005.
https://arxiv.org/abs/astro-ph/0604171

[radius2-10] Calculated, using the Stefan-Boltzmann law and the star's effective temperature and luminosity, with respect to the solar nominal effective temperature of 5,772 K: ${\sqrt {{\biggl (}{\frac {5,772}{5,171}}{\biggr )}^{4}\cdot 10^{-0.49}}}=0.709\ R_{\odot }.$

[SIMBAD-1] ^ ^a ^b ^c ^d ^e ^f "SIMBAD Astronomical Database". Centre de Données astronomiques de Strasbourg. Retrieved 2013-08-23.

A: LHS 437 -- High proper-motion Star

B: LHS 438 -- High proper-motion Star

C: V* V2215 Oph -- Variable of RS CVn type

[3] A: LHS 437 -- High proper-motion Star

[4] B: LHS 438 -- High proper-motion Star

[5] C: V* V2215 Oph -- Variable of RS CVn type

[GaiaEDR3a-2] 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.

[GaiaEDR3b-3] 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.

[GaiaEDR3c-4] 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.

[Tokovinin2017-5] Tokovinin, Andrei (July 2017). "Orbit Alignment in Triple Stars". The Astrophysical Journal. 844 (2): 103. arXiv:1706.00748. Bibcode:2017ApJ...844..103T. doi:10.3847/1538-4357/aa7746. ISSN 0004-637X.

[Luck2017-6] Luck, R. Earle (2017-01-01). "Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants". The Astronomical Journal. 153 (1): 21. arXiv:1611.02897. Bibcode:2017AJ....153...21L. doi:10.3847/1538-3881/153/1/21. ISSN 0004-6256.36 Ophiuchi A's database entry at VizieR.

[aaa505_1_205-7] Demory, Brice-Olivier; Ségransan, Damien; Forveille, Thierry; Queloz, Didier; Beuzit, Jean-Luc; Delfosse, Xavier; Di Folco, Emmanuel; Kervella, Pierre; Le Bouquin, Jean-Baptiste; Perrier, Christian; Benisty, Myriam; Duvert, Gilles; Hofmann, Karl-Heinz; Lopez, Bruno; Petrov, Romain (October 2009). "Mass-radius relation of low and very low-mass stars revisited with the VLTI". Astronomy and Astrophysics. 505 (1): 205–215. arXiv:0906.0602. Bibcode:2009A&A...505..205D. doi:10.1051/0004-6361/200911976. S2CID 14786643.

[Hardegree-Ullman2023-8] Hardegree-Ullman, Kevin K.; Apai, Dániel; Bergsten, Galen J.; Pascucci, Ilaria; López-Morales, Mercedes (2023-06-01). "Bioverse: A Comprehensive Assessment of the Capabilities of Extremely Large Telescopes to Probe Earth-like O2 Levels in Nearby Transiting Habitable-zone Exoplanets". The Astronomical Journal. 165 (6): 267. arXiv:2304.12490. Bibcode:2023AJ....165..267H. doi:10.3847/1538-3881/acd1ec. ISSN 0004-6256. 36 Ophiuchi A's database entry at VizieR.

[Luck2018-9] ^ ^a ^b ^c ^d ^e ^f ^g Luck, R. Earle (2018-03-01). "Abundances in the Local Region. III. Southern F, G, and K Dwarfs". The Astronomical Journal. 155 (3): 111. Bibcode:2018AJ....155..111L. doi:10.3847/1538-3881/aaa9b5. ISSN 0004-6256. 36 Ophiuchi B's database entry at VizieR.

[11] Garg, Suyog; Karak, Bidya Binay; Egeland, Ricky; Soon, Willie; Baliunas, Sallie (2019), "Waldmeier Effect in Stellar Cycles", The Astrophysical Journal, 886 (2): 132, arXiv:1909.12148, Bibcode:2019ApJ...886..132G, doi:10.3847/1538-4357/ab4a17, S2CID 202888617

[ASAS-SN-12] "ASAS-SN Variable Stars Database". ASAS-SN Variable Stars Database. ASAS-SN. Retrieved 6 January 2022.

[WGSN-13] "IAU Working Group on Star Names (WGSN)". Retrieved 17 September 2018.

[IAU-CSN-14] "IAU Catalog of Star Names". International Astronomical Union. Retrieved 2018-09-17.

[search-15] Wittenmeyer et al. (2006).

[Irwin-16] Irwin et al. (1996).

[Nasa2019-03-07-17] Bill Steigerwald (2019-03-07). ""Goldilocks" Stars May Be "Just Right" for Finding Habitable Worlds". NASA. Retrieved 2020-05-12. 'I find that certain nearby K stars like 61 Cyg A/B, Epsilon Indi, Groombridge 1618, and HD 156026 may be particularly good targets for future biosignature searches,' said Arney.

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