Nu Octantis
  | |
| Observation data EpochJ2000EquinoxJ2000 | |
|---|---|
| Constellation | Octans |
| Right ascension | 21h41m28.64977s[1] |
| Declination | −77° 23′ 24.1563″[1] |
| Apparent magnitude(V) | 3.73[2] |
| Characteristics | |
| A | |
| Evolutionary stage | Giant star |
| Spectral type | K1III[3] |
| U−Bcolor index | +0.89[4] |
| B−Vcolor index | +1.00[4] |
| B | |
| Evolutionary stage | Either a main sequence star or awhite dwarf[5] |
| Spectral type | K7–M0V or WD[5] |
| Astrometry | |
| Radial velocity(Rv) | +34.40[6]km/s |
| Proper motion(μ) | RA:+68.656mas/yr[7] Dec.:−250.044mas/yr[7] |
| Parallax(π) | 51.5172 ± 0.6525mas[7] |
| Distance | 63.3 ± 0.8ly (19.4 ± 0.2pc) |
| Absolute magnitude(MV) | 2.3±0.16[5] |
| Orbit[8] | |
| Period(P) | 1050.69+0.05 −0.07d |
| Semi-major axis(a) | 2.62959+0.00009 −0.00011AU |
| Eccentricity(e) | 0.23680±0.00007 |
| Inclination(i) | 70.8±0.9° |
| Longitude of the node(Ω) | 87±1.2° |
| Argument of periastron(ω) (secondary) | 74.970±0.016° |
| Semi-amplitude(K1) (primary) | 7.032±0.003km/s |
| Details | |
| Nu Octantis A | |
| Mass | 1.04[9] 1.61[8]M☉ |
| Radius | 5.9[9] 5.81±0.12[8]R☉ |
| Luminosity | 17.53[2]L☉ |
| Surface gravity(logg) | 3.12±0.10[8]cgs |
| Temperature | 4,860±40[10]K |
| Metallicity[Fe/H] | +0.18±0.04[8]dex |
| Rotational velocity(vsini) | 2.0[8]km/s |
| Age | ~2.5-3[8]Gyr |
| Nu Octantis B[5] | |
| Mass | 0.585[8]M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
ν Octantis,LatinisedasNu Octantis,is a star in theconstellationofOctans.Unusually, it is the brightest star in this faint constellation atapparent magnitude+3.7.[2]It is aspectroscopic binary[11]starwith a period around 2.9 years.[10]Parallaxmeasurements place it at 19.4 parsecs (63 ly) from Earth.[7]
The primary has aspectral typeof K1III,[3]with theluminosity classIII indicating that it is agiant starthat has burned up thehydrogenat its core and has expanded. Nu Octantis A has 1.6 times themass of the Sun,but has expanded to 5.8 times theradius of the Sun.[8]Itsphotospherehas cooler to aneffective temperatureof 4,860K[10]and now is radiating 18 times as much luminosity as the Sun.[2]It possibly hosts anextrasolar planet,ajovian planeton a retograde orbit.[5]
The secondary star is likely either ared dwarfor awhite dwarf,from its relatively low mass.[5]This star is estimated to have around 60% the mass of the Sun. It shares acenter of masswith the primary, completing an orbit around it every 2 years and 11 months. The orbit has aneccentricityof 0.24 and asemi-major axisof 2.63au.[8]
Planetary system
[edit]In 2009, the system was hypothesised to contain asuperjovianexoplanetbased on perturbations in the orbital period.[10]Aprogradesolution was quickly ruled out[12]but aretrogradesolution remains a possibility, although the variations may instead be due to the secondary star being itself a close binary,[13]since the formation of a planet in such a system would be difficult due to dynamic perturbations.[14]Further evidence ruling out a stellar variability and favouring the existence of the planet was gathered by 2021.[5]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 2.1059MJ | 1.276 | 414.8 | 0.086 | 112.5° | — |
See also
[edit]- Gamma CepheiandNu2Canis Majoris,another similar-sized giant stars hosting a jovian planet
- Beta Hydri
References
[edit]- ^abVan Leeuwen, F. (2007). "Validation of the new Hipparcos reduction".Astronomy and Astrophysics.474(2): 653–664.arXiv:0708.1752.Bibcode:2007A&A...474..653V.doi:10.1051/0004-6361:20078357.S2CID18759600.Vizier catalog entry
- ^abcdAnderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation".Astronomy Letters.38(5): 331.arXiv:1108.4971.Bibcode:2012AstL...38..331A.doi:10.1134/S1063773712050015.S2CID119257644.Vizier catalog entry
- ^abGray, R. O.; et al. (July 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.S2CID119476992.
- ^abMallama, A. (2014). "Sloan Magnitudes for the Brightest Stars".The Journal of the American Association of Variable Star Observers.42(2): 443.Bibcode:2014JAVSO..42..443M.Vizier catalog entry
- ^abcdefgRamm, D J; Robertson, P; et al. (2021)."A photospheric and chromospheric activity analysis of the quiescent retrograde-planet host ν Octantis A".Monthly Notices of the Royal Astronomical Society.502(2): 2793–2806.arXiv:2101.06844.doi:10.1093/mnras/stab078.
- ^Wilson, R. E. (1953). "General Catalogue of Stellar Radial Velocities".Carnegie Institute Washington D.C. Publication.Carnegie Institution for Science.Bibcode:1953GCRV..C......0W.LCCN54001336.
- ^abcBrown, A. G. A.;et al. (Gaia collaboration) (August 2018)."GaiaData Release 2: Summary of the contents and survey properties ".Astronomy & Astrophysics.616.A1.arXiv:1804.09365.Bibcode:2018A&A...616A...1G.doi:10.1051/0004-6361/201833051.Gaia DR2 record for this sourceatVizieR.
- ^abcdefghijkRamm, D. J.; et al. (2016)."The conjectured S-type retrograde planet in ν Octantis: more evidence including four years of iodine-cell radial velocities".Monthly Notices of the Royal Astronomical Society.460(4): 3706–3719.arXiv:1605.06720.Bibcode:2016MNRAS.460.3706R.doi:10.1093/mnras/stw1106.
- ^abAllende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures".Astronomy and Astrophysics.352:555–562.arXiv:astro-ph/9911002.Bibcode:1999A&A...352..555A.Vizier catalog entry
- ^abcdRamm, D. J.; Pourbaix, D.; Hearnshaw, J. B.; Komonjinda, S. (April 2009)."Spectroscopic orbits for K giants β Reticuli and ν Octantis: what is causing a low-amplitude radial velocity resonant perturbation in ν Oct?".Monthly Notices of the Royal Astronomical Society.394(3): 1695–1710.Bibcode:2009MNRAS.394.1695R.doi:10.1111/j.1365-2966.2009.14459.x.
- ^Eggleton, P. P.; Tokovinin, A. A. (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.S2CID14878976.
- ^Eberle, J.; Cuntz, M. (October 2010)."On the reality of the suggested planet in the ν Octantis system".The Astrophysical Journal.721(2): L168–L171.Bibcode:2010ApJ...721L.168E.doi:10.1088/2041-8205/721/2/L168.
- ^Morais, M. H. M.; Correia, A. C. M. (February 2012)."Precession due to a close binary system: an alternative explanation for ν-Octantis?".Monthly Notices of the Royal Astronomical Society.419(4): 3447–3456.arXiv:1110.3176.Bibcode:2012MNRAS.419.3447M.doi:10.1111/j.1365-2966.2011.19986.x.S2CID119152109.
- ^Gozdziewski, K.; Slonina, M.; Migaszewski, C.; Rozenkiewicz, A. (March 2013)."Testing a hypothesis of the ν Octantis planetary system".Monthly Notices of the Royal Astronomical Society.430(1): 533–545.arXiv:1205.1341.Bibcode:2013MNRAS.430..533G.doi:10.1093/mnras/sts652.
