HD 2638
View on Wikipedia| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Cetus[1] |
| Right ascension | 00h 29m 59.8721s[2] |
| Declination | −05° 45′ 50.399″[2] |
| Apparent magnitude (V) | 9.44[3] |
| Characteristics | |
| Spectral type | K1V[4] (G8V + M1V)[5] |
| B−V color index | +0.886±0.003[3] |
| Astrometry | |
| Radial velocity (Rv) | +9.576±0.0010[2] km/s |
| Proper motion (μ) | RA: −107.019±0.094[2] mas/yr Dec.: −223.039±0.062[2] mas/yr |
| Parallax (π) | 18.1656±0.0510 mas[2] |
| Distance | 179.5 ± 0.5 ly (55.0 ± 0.2 pc) |
| Absolute magnitude (MV) | 5.96[3] |
| Orbit[6] | |
| Primary | HD 2638 A |
| Name | HD 2638 BC |
| Period (P) | 130 yr |
| Semi-major axis (a) | 25.5±1.9 AU |
| Details[7] | |
| A | |
| Mass | 0.89±0.02 M☉ |
| Radius | 0.8±0.01 R☉ |
| Luminosity | 0.407±0.004 L☉ |
| Surface gravity (log g) | 4.58±0.02 cgs |
| Temperature | 5,160±24 K |
| Metallicity [Fe/H] | 0.12±0.05[8] dex |
| Age | 1.9±2.6 Gyr |
| BC | |
| Mass | 0.425±0.067[5] M☉ |
| Radius | 0.46±0.02[5] R☉ |
| Luminosity | 0.030±0.005[5] L☉ |
| Surface gravity (log g) | 4.80±0.02[5] cgs |
| Temperature | 3571±48[5] K |
| Other designations | |
| BD−06°82, HD 2638, HIP 2350, WDS J00293-0555BC, NLTT 1594, 2MASS J00295988-0545502, Gaia DR2 2526925389919277056[9] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
HD 2638 is a ternary star system[10] system in the equatorial constellation of Cetus. The pair have an angular separation of 0.53″ along a position angle of 166.7°, as of 2015.[10] This is system too faint to be visible to the naked eye, having a combined apparent visual magnitude of 9.44;[3] a small telescope is required. The distance to this system is 179.5 light years based on parallax, and it is drifting further away with a radial velocity of +9.6 km/s.[2] The magnitude 7.76 star HD 2567 forms a common proper motion companion to this pair[10] at projected separation 839″.[6]
The HD 2638 members A and BC have a projected separation of about 25.5±1.9 AU and thus an orbital period of around 130 years.[5] They have a combined stellar classification of K1V.[4] The primary component is a G-type main-sequence star with a class of G8V.[5] It is smaller and less massive than the Sun, and has a lower luminosity.[7] The secondary is a binary consisting of two red dwarf stars on close orbit with combined mass less than half the mass of the primary, and a composite spectral class of M1V.[5]
Planetary system
[edit]In 2005, the discovery of an extrasolar planet HD 2638 b orbiting the primary was announced by the Geneva Extrasolar Planet Search Team. The planet has a mass 0.48 times that of Jupiter and 152.6 times that of Earth.[11] The planet existence was placed under doubt in 2015 due to discovered additional stellar companions.[6]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination (°) |
Radius |
|---|---|---|---|---|---|---|
| b | >0.48 MJ | 0.044 | 3.4442±0.0002 | 0.0407 | — | — |
See also
[edit]References
[edit]- ^ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
- ^ a b c d e f g Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data 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 source at VizieR.
- ^ a b c d Anderson, 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. S2CID 119257644.
- ^ a b Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
- ^ a b c d e f g h i Wittrock, Justin M.; et al. (November 2016). "Stellar Companions to the Exoplanet Host Stars HD 2638 and HD 164509". The Astronomical Journal. 152 (5): 7. arXiv:1609.00016. Bibcode:2016AJ....152..149W. doi:10.3847/0004-6256/152/5/149. S2CID 45942803. 149.
- ^ a b c Roberts Jr, Lewis C.; Tokovinin, Andrei; Mason, Brian D.; Riddle, Reed L.; Hartkopf, William I.; Law, Nicholas M.; Baranec, Christoph (2015), "Know the Star, Know the Planet. III. Discovery of Late-Type Companions to Two Exoplanet Host Stars", The Astronomical Journal, 149 (4): 118, arXiv:1503.01211, Bibcode:2015AJ....149..118R, doi:10.1088/0004-6256/149/4/118, S2CID 30908636
- ^ a b Bonfanti, A.; et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics. 575. A18. arXiv:1411.4302. Bibcode:2015A&A...575A..18B. doi:10.1051/0004-6361/201424951. S2CID 54555839.
- ^ Tsantaki, M.; Sousa, S. G.; Adibekyan, V. Zh.; Santos, N. C.; Mortier, A.; Israelian, G. (2013). "Deriving precise parameters for cool solar-type stars. Optimizing the iron line list". Astronomy and Astrophysics. 555. arXiv:1304.6639. Bibcode:2013A&A...555A.150T. doi:10.1051/0004-6361/201321103.
- ^ "HD 2638". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2011-12-20.
- ^ a b c Riddle, Reed L.; et al. (January 2015). "A Survey of the High Order Multiplicity of Nearby Solar-type Binary Stars with Robo-AO". The Astrophysical Journal. 799 (1): 21. arXiv:1411.0682. Bibcode:2015ApJ...799....4R. doi:10.1088/0004-637X/799/1/4. S2CID 5642378. 4.
- ^ a b Moutou, C.; et al. (2015). "The HARPS search for southern extra-solar planets IV. Three close-in planets around HD 2638, HD 27894 and HD 63454". Astronomy and Astrophysics. 439 (1): 367–373. arXiv:1411.7048. Bibcode:2005A&A...439..367M. doi:10.1051/0004-6361:20052826.
