HD 47366 is the Henry Draper Catalogue designation for a star in the southern constellation of Canis Major. It has an apparent visual magnitude of 6.12,[2] which puts it near the lower limit of stars visible to the naked eye. According to the Bortle scale, it can be viewed from dark rural skies. Parallax measurements performed by the Gaia spacecraft provide a distance estimate of 276 light-years (85 parsecs).[1]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Canis Major |
| Right ascension | 06h 37m 40.793s[1] |
| Declination | −12° 59′ 06.42″[1] |
| Apparent magnitude (V) | 6.12[2] |
| Characteristics | |
| Spectral type | K1III:[3] |
| B−V color index | 0.977[3] |
| Astrometry | |
| Radial velocity (Rv) | 9.01[3] km/s |
| Proper motion (μ) | RA: 10.239 mas/yr[1] Dec.: −125.836 mas/yr[1] |
| Parallax (π) | 11.8263 ± 0.0636 mas[1] |
| Distance | 276 ± 1 ly (84.6 ± 0.5 pc) |
| Absolute magnitude (MV) | 1.459[3] |
| Details | |
| Mass | 1.81±0.13[4] M☉ |
| Radius | 7.30±0.33[4] R☉ |
| Luminosity | 26.1±1.8[4] L☉ |
| Surface gravity (log g) | 2.60[3] cgs |
| Temperature | 4,772[3] K |
| Metallicity [Fe/H] | −0.16[3] dex |
| Rotation | < 86[4] d |
| Rotational velocity (v sin i) | 4.3±0.8[4] km/s |
| Age | 1.61±0.53[4] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is a K-type giant star with a stellar classification of K1III: − the colon suffix indicates some uncertainty in the luminosity classification of III.[3] Spectroscopic analysis of the star was used to derive an estimated mass of about 1.81 times the mass of the Sun. It has an estimated age of 1.6 billion years; old enough at that mass to have evolved off the main sequence. As a giant star, the atmosphere has expanded to 7.3 times the Sun's radius, and it is emitting 26 times the solar luminosity at an effective temperature of 4,772 K. The projected rotational velocity of the star is 4.3 km/s, indicating it is rotating with a period of under 86 days.[4]
In 2016, a team of astronomers reported the detection of a pair of giant planetary companions. Radial velocity measurements indicated gravitational perturbations of the star being caused by orbiting objects. The best fit to the preliminary data suggests two periodicities: one almost exactly a year long like the Earth's periodicity, and a second of around two years. Both objects are predicted to have masses greater than that of the planet Jupiter: their minimum masses are 1.8 and 1.9 Jupiter masses, respectively. Until the inclination of their orbits is known, their actual masses cannot be pinned down more accurately.[4]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥ 1.75+0.20 −0.17 MJ |
1.214+0.030 −0.029 |
363.3+2.5 −2.4 |
0.089+0.079 −0.060 |
— | — |
| c | ≥ 1.86+0.16 −0.15 MJ |
1.853+0.045 −0.045 |
684.7+5.0 −4.9 |
0.278+0.069 −0.094 |
— | — |
Modelling of the orbits of the two planets showed that they are dynamically unstable on the life span of their host star unless they are in a 2:1 mean motion resonance or are on mutually retrograde orbits.[4] In 2019, J. P. Marshall and associates proposed an orbital fit with lower eccentricities that is more stable. The new fit is closer to the 2:1 mean motion resonance. As the host star continues to evolve to a larger radius, it is expected that both planets will undergo orbital decay due to tidal forces and be engulfed.[6]
References
edit- ^ 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 Corben, P. M.; Stoy, R. H. (1968), "Photoelectric Magnitudes and Colours for Bright Southern Stars", Monthly Notes of the Astronomical Society of Southern Africa, 27: 11, Bibcode:1968MNSSA..27...11C.
- ^ a b c d e f g h Soubiran, C.; et al. (March 2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics, 480 (1): 91–101, arXiv:0712.1370, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788, S2CID 16602121.
- ^ a b c d e f g h i j Sato, Bun'ei; et al. (January 18, 2016), "A Pair of Giant Planets around the Evolved Intermediate-Mass Star HD 47366: Multiple Circular Orbits or a Mutually Retrograde Configuration", The Astrophysical Journal, 819 (1): 59, arXiv:1601.04417, Bibcode:2016ApJ...819...59S, doi:10.3847/0004-637X/819/1/59, S2CID 118535422.
- ^ "HD 47366". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-01-21.
- ^ Marshall, J. P.; et al. (January 2019), "Re-analyzing the Dynamical Stability of the HD 47366 Planetary System", The Astronomical Journal, 157 (1): 11, arXiv:1811.06476, Bibcode:2019AJ....157....1M, doi:10.3847/1538-3881/aaef32, S2CID 119449335, 1
External links
edit- Nowakowski, Tomasz (January 21, 2016), "Two giant planets detected around an evolved intermediate-mass star", Physorg.org.