Mu2 Octantis

For other stars with this Bayer designation, see μ Octantis.
Mu2 Octantis
Location of μ2 Octantis (circled in red)
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Octans
μ2 Oct A
Right ascension 20h 41m 44.1016s[1]
Declination −75° 21′ 02.883″[1]
Apparent magnitude (V) +6.481±0.007[2]
μ2 Oct B
Right ascension 20h 41m 45.5181s[3]
Declination −75° 20′ 47.047″[3]
Apparent magnitude (V) +7.153±0.011[2]
Characteristics
μ2 Oct A
Spectral type G1V[4]
U−B color index +0.26[5]
B−V color index +0.62[5]
μ2 Oct B
Spectral type G1V[6]
Astrometry
μ2 Oct A
Radial velocity (Rv)−11.00±0.12[1] km/s
Proper motion (μ) RA: 156.404 mas/yr[1]
Dec.: −162.214 mas/yr[1]
Parallax (π)25.0327±0.0205 mas[1]
Distance130.3 ± 0.1 ly
(39.95 ± 0.03 pc)
Absolute magnitude (MV)3.28[4]
μ2 Oct B
Radial velocity (Rv)−10.94±0.15[3] km/s
Proper motion (μ) RA: +163.531 mas/yr[3]
Dec.: −171.346 mas/yr[3]
Parallax (π)25.0379±0.0167 mas[3]
Distance130.27 ± 0.09 ly
(39.94 ± 0.03 pc)
Orbit[4]
Semi-major axis (a)932 AU
Details[7]
μ2 Oct A
Mass1.330±0.013 M☉
Radius1.730+0.044
−0.039 R☉
Luminosity3.54+0.27
−0.20[8] L☉
Surface gravity (log g)4.09±0.02[8] cgs
Temperature6,059±52 K
Metallicity [Fe/H]+0.216±0.009 dex
Rotation22.5±2.9[8] days
Rotational velocity (v sin i)1.45[4] km/s
Age3.50+0.65
−0.27 Gyr
μ2 Oct B
Mass1.190+0.017
−0.018 M☉
Radius1.190+0.034
−0.010 R☉
Temperature6,020±52 K
Metallicity [Fe/H]+0.267±0.009 dex
Age2.10+1.03
−0.34 Gyr
Other designations
μ2 Oct, CCDM J20417-7521
μ2 Oct A: CD−75°1173, HD 196067, HIP 102125, HR 7864, SAO 257836, 2MASS J20414409-7521029
μ2 Oct B: CD−75°1174, HD 196068, HIP 102128, SAO 257837, 2MASS J20414550-7520471
Database references
SIMBADA
B
Exoplanet Archivedata

Mu2 Octantis (μ2 Oct) is a binary star system in the constellation Octans, whose primary and secondary stars have apparent magnitudes of +6.481 and 7.153, respectively.[2] Based on parallax measurements, it lies 130.3 light-years away.[1][3]

The two stars, HD 196067 and HD 196068 (also named μ2 Oct A and μ2 Oct B), are separated at 17 arcseconds in the sky, corresponding to 740 astronomical units (AU). The semimajor axis of the stars' orbit is 932 AU.[4]

Component A is a G-dwarf star with 1.33 and 1.73 times of the Sun's mass and radius, respectively. Component B also a G-type main-sequence star with a radius 1.19 times larger than the Sun. Their effective temperatures are similar. HD 196068 has a higher metallicity than its companion, the reasons for this are uncertain.[7]

Planetary system

From 1998 to 2012, the system was observed using the CORALIE instrument, at the ESO's La Silla Observatory.[4]

In November 2012, a long-period, wide-orbiting planet was deduced by radial velocity around HD 196067. The planet has been pulled to an eccentric orbit by the B star HD 196068. The planet's true mass, as measured by astrometry, is 12.5 MJ, placing it right on the traditionally adopted boundary between planets and brown dwarfs.[9]

A second, innermost planet was detected using radial velocity observations with the CORALIE, HARPS, and ESPRESSO observatories. Despite its small orbit, it does not transit the host star.[8]

The μ2 Oct A planetary system[8]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination
(°) 		Radius
c ≥10.4±1.39 M🜨 — 4.601088±0.000192 0.235±0.118 — —
b 11.4±1.6 MJ 4.71+0.11
−0.10 		3,413.7±10.5 0.56292±0.00703 29.7+5.0
−3.8 		—

References

  1. ^ a b c d e f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c Paunzen, E. (2015-08-01). "A new catalogue of Strömgren-Crawford uvbyβ photometry". Astronomy and Astrophysics. 580: A23. arXiv:1506.04568. Bibcode:2015A&A...580A..23P. doi:10.1051/0004-6361/201526413. ISSN 0004-6361.
  3. ^ a b c d e f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  4. ^ a b c d e f Marmier, M.; et al. (2013). "The CORALIE survey for southern extrasolar planets XVII. New and updated long period and massive planets". Astronomy and Astrophysics. 551. A90. arXiv:1211.6444. Bibcode:2013A&A...551A..90M. doi:10.1051/0004-6361/201219639. S2CID 59467665.
  5. ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  6. ^ Gray, R. O.; et al. (2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc—The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 119476992.
  7. ^ a b Flores, M; Yana Galarza, J; Miquelarena, P; Saffe, C; Jaque Arancibia, M; Ibañez Bustos, R V; Jofré, E; Alacoria, J; Gunella, F (2023-12-06). "Elemental abundance differences in the massive planet-hosting wide binary HD 196067−68". Monthly Notices of the Royal Astronomical Society. 527 (4): 10016–10024. arXiv:2311.17272. doi:10.1093/mnras/stad3714. ISSN 0035-8711.
  8. ^ a b c d e Delisle, J.-B.; Faria, J. P.; Ségransan, D.; Fontanet, E.; Ceva, W.; Barbato, D.; Sousa, S. G.; Unger, N.; Leleu, A. (2025-09-30). "Architecture of planetary systems with and without outer giant planets I. Inner planet detections around HD 23079, HD 196067, and HD 86226". Astronomy & Astrophysics. arXiv:2509.26232.
  9. ^ Li, Yiting; Brandt, Timothy D.; Brandt, G. Mirek; Dupuy, Trent J.; Michalik, Daniel; Jensen-Clem, Rebecca; Zeng, Yunlin; Faherty, Jacqueline; Mitra, Elena L. (2021). "Precise Masses and Orbits for Nine Radial-velocity Exoplanets". The Astronomical Journal. 162 (6): 266. arXiv:2109.10422. Bibcode:2021AJ....162..266L. doi:10.3847/1538-3881/ac27ab. S2CID 237592581.

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