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]
| 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
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
