HD 221420
HD 221420 (HR 8935; Gliese 4340) is a likely binary star system[7] in the southern circumpolar constellation Octans. It has an apparent magnitude of 5.81, allowing it to be faintly seen with the naked eye. The object is relatively close at a distance of 102 light years but is receding with a heliocentric radial velocity of 26.5 km/s.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Octans |
| Right ascension | 23h 33m 19.5789s[1] |
| Declination | −77° 23′ 07.194″[1] |
| Apparent magnitude (V) | 5.81±0.01[2] |
| Characteristics | |
| Spectral type | G2 IV-V[3] |
| U−B color index | +0.31[4] |
| B−V color index | +0.68[4] |
| Astrometry | |
| Radial velocity (Rv) | 26.48±0.02[5] km/s |
| Proper motion (μ) | RA: +16.306 mas/yr[1] Dec.: +0.736 mas/yr[1] |
| Parallax (π) | 32.1023 ± 0.0325 mas[1] |
| Distance | 101.6 ± 0.1 ly (31.15 ± 0.03 pc) |
| Absolute magnitude (MV) | +3.33[6] |
| Details | |
| Mass | 1.35±0.01[7] M☉ |
| Radius | 1.95±0.01[7] R☉ |
| Luminosity | 4.01±1[8] L☉ |
| Surface gravity (log g) | 4.03±0.03[7] cgs |
| Temperature | 5,830±44[9] K |
| Metallicity [Fe/H] | +0.34±0.07[10] dex |
| Rotational velocity (v sin i) | 2.8±0.5[11] km/s |
| Age | 3.65±0.23[7] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
| Extrasolar Planets Encyclopaedia | data |
HD 221420 has a stellar classification of G2 IV-V,[3] indicating a solar analogue with a luminosity class intermediate between a subgiant and a main sequence star. The object is also extremely chromospherically inactive.[3] It has a comparable mass to the Sun and a diameter of 1.95 R☉.[7] It shines with a luminosity of 4 L☉[8] from its photosphere at an effective temperature of 5,830 K,[9] giving a yellow glow. HD 221420 is younger than the Sun at 3.65 billion years.[7] Despite this, the star is already beginning to evolve off the main sequence. Like most planetary hosts, HD 221420 has a metallicity over twice of that of the Sun[7] and spins modestly with a projected rotational velocity 2.8 km/s.[11]
There is a mid-M-dwarf star with a similar proper motion and parallax to HD 221420, which is likely gravitationally bound to it. The two stars are separated by 698 arcseconds, corresponding to a distance of 21,756 AU.[7]
Planetary system
In a 2019 doppler spectroscopy survey, an exoplanet was discovered orbiting the star. The planet was originally thought to be a super Jupiter, having a minimum mass of 9.7 MJ.[9] However, later observations using Hipparcos and Gaia astrometry found it to be a brown dwarf with a high-inclination orbit,[7][10][14] revealing a true mass of 23 MJ.[7]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (years) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 22.9±2.2 MJ | 10.15+0.59 −0.38 | 27.62+2.45 −1.54 | 0.14+0.04 −0.03 | 164.0+1.9 −2.6° | — |
References
- ^ a b c d Vallenari, A.; et al. (Gaia Collaboration) (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. arXiv:2208.00211. doi:10.1051/0004-6361/202243940. Gaia DR3 record for this source at VizieR.
- ^ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
- ^ a b c Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Bubar, E. J.; McGahee, C. E.; O'Donoghue, A. A.; Knox, E. R. (2 June 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. eISSN 1538-3881. ISSN 0004-6256.
- ^ a b Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
- ^ Jofré, E.; Petrucci, R.; Saffe, C.; Saker, L.; Artur de la Villarmois, E.; Chavero, C.; Gómez, M.; Mauas, P. J. D. (26 January 2015). "Stellar parameters and chemical abundances of 223 evolved stars with and without planets". Astronomy & Astrophysics. 574: A50. arXiv:1410.6422. Bibcode:2015A&A...574A..50J. doi:10.1051/0004-6361/201424474. eISSN 1432-0746. ISSN 0004-6361.
- ^ Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. ISSN 1063-7737. S2CID 119257644.
- ^ a b c d e f g h i j k l Venner, Alexander; Vanderburg, Andrew; Pearce, Logan A. (11 June 2021). "True Masses of the Long-period Companions to HD 92987 and HD 221420 from Hipparcos–Gaia Astrometry". The Astronomical Journal. 162 (1): 12. arXiv:2104.13941. Bibcode:2021AJ....162...12V. doi:10.3847/1538-3881/abf932. eISSN 1538-3881. ISSN 0004-6256.
- ^ a b 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 Kane, Stephen R.; Dalba, Paul A.; Li, Zhexing; Horch, Elliott P.; Hirsch, Lea A.; Horner, Jonathan; Wittenmyer, Robert A.; Howell, Steve B.; Everett, Mark E.; Butler, R. Paul; Tinney, Christopher G.; Carter, Brad D.; Wright, Duncan J.; Jones, Hugh R. A.; Bailey, Jeremy; O'Toole, Simon J. (5 June 2019). "Detection of Planetary and Stellar Companions to Neighboring Stars via a Combination of Radial Velocity and Direct Imaging Techniques". The Astronomical Journal. 157 (6): 252. arXiv:1904.12931. Bibcode:2019AJ....157..252K. doi:10.3847/1538-3881/ab1ddf. eISSN 1538-3881.
- ^ a b Li, Yiting; Brandt, Timothy D.; Brandt, G. Mirek; Dupuy, Trent J.; Michalik, Daniel; Jensen-Clem, Rebecca; Zeng, Yunlin; Faherty, Jacqueline; Mitra, Elena L. (26 November 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. eISSN 1538-3881. ISSN 0004-6256.
- ^ a b Valenti, Jeff A.; Fischer, Debra A. (July 2005). "Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs". The Astrophysical Journal Supplement Series. 159 (1): 141–166. Bibcode:2005ApJS..159..141V. doi:10.1086/430500. eISSN 1538-4365. ISSN 0067-0049.
- ^ Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
- ^ "HR 8935". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved July 15, 2022.
- ^ Feng, Fabo; Butler, R. Paul; et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series. 262 (21): 21. arXiv:2208.12720. Bibcode:2022ApJS..262...21F. doi:10.3847/1538-4365/ac7e57. S2CID 251864022.