HD 2638 is a ternary star system[9] 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.[9] This is system too faint to be visible to the naked eye, having a combined apparent visual magnitude of 9.44;[2] 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.[1] The magnitude 7.76 star HD 2567 forms a common proper motion companion to this pair[9] at projected separation 839″.[5]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cetus |
| Right ascension | 00h 29m 59.8721s[1] |
| Declination | –05° 45′ 50.3987″[1] |
| Apparent magnitude (V) | 9.44[2] |
| Characteristics | |
| Spectral type | K1V[3] (G8V + M1V)[4] |
| B−V color index | +0.886±0.003[2] |
| Astrometry | |
| Radial velocity (Rv) | +9.576±0.0010[1] km/s |
| Proper motion (μ) | RA: −107.019±0.094[1] mas/yr Dec.: −223.039±0.062[1] mas/yr |
| Parallax (π) | 18.1656 ± 0.0510 mas[1] |
| Distance | 179.5 ± 0.5 ly (55.0 ± 0.2 pc) |
| Absolute magnitude (MV) | 5.96[2] |
| Orbit[5] | |
| Primary | HD 2638 A |
| Companion | HD 2638 BC |
| Period (P) | 130 yr |
| Semi-major axis (a) | 25.5±1.9 AU |
| Details[6] | |
| 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[7] dex |
| Age | 1.9±2.6 Gyr |
| BC | |
| Mass | 0.425±0.067[4] M☉ |
| Radius | 0.46±0.02[4] R☉ |
| Luminosity | 0.030±0.005[4] L☉ |
| Surface gravity (log g) | 4.80±0.02[4] cgs |
| Temperature | 3571±48[4] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
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.[4] They have a combined stellar classification of K1V.[3] The primary component is a G-type main-sequence star with a class of G8V.[4] It is smaller and less massive than the Sun, and has a lower luminosity.[6] The secondary is a binary consisting of who red dwarf stars on close orbit with combined mass less than half the mass of the primary, and a composite spectral class of M1V.[4]
Planetary system
editIn 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.[10] The planet existence was placed under doubt in 2015 due to discovered additional stellar companions.[5]
| 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
editReferences
edit- ^ 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.
- ^ Tsantaki1, M.; Sousa, S. G.; Adibekyan, V. Zh.; Santos, N. C.; Mortier, A.; Israelian, G. (July 2013). "Deriving precise parameters for cool solar-type stars Optimizing the iron line list". Astronomy & Astrophysics. 555: 11. arXiv:1304.6639. Bibcode:2013A&A...555A.150T. doi:10.1051/0004-6361/201321103. S2CID 118388752. A150.
{{cite journal}}: CS1 maint: numeric names: authors list (link) - ^ "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.