Astronomy:HD 221420
| Observation data Epoch J2000.0 Equinox (celestial coordinates) | |
|---|---|
| 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[1] mas/yr Dec.: +0.736[1] mas/yr |
| Parallax (π) | 32.1023 ± 0.0325[1] mas |
| 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 (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.
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 solar luminosity[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 astronomical unit|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 Jupiter mass.[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 Jupiter mass.[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
- ↑ 1.0 1.1 1.2 1.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. 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. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H.
- ↑ 3.0 3.1 3.2 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. doi:10.1086/504637. ISSN 0004-6256. Bibcode: 2006AJ....132..161G.
- ↑ 4.0 4.1 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. doi:10.1051/0004-6361/201424474. ISSN 0004-6361. Bibcode: 2015A&A...574A..50J.
- ↑ Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation" (in en). Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode: 2012AstL...38..331A.
- ↑ 7.00 7.01 7.02 7.03 7.04 7.05 7.06 7.07 7.08 7.09 7.10 7.11 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. doi:10.3847/1538-3881/abf932. ISSN 0004-6256. Bibcode: 2021AJ....162...12V.
- ↑ 8.0 8.1 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. Gaia DR2 record for this source at VizieR.
- ↑ 9.0 9.1 9.2 Kane, Stephen R.; Dalba, Paul A.; Li, Zhexing; Horch, Elliott P.; Hirsch, Lea A.; Horner, Jonathan; Wittenmyer, Robert A.; Howell, Steve B. et al. (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. doi:10.3847/1538-3881/ab1ddf. Bibcode: 2019AJ....157..252K.
- ↑ 10.0 10.1 Li, Yiting; Brandt, Timothy D.; Brandt, G. Mirek; Dupuy, Trent J.; Michalik, Daniel; Jensen-Clem, Rebecca; Zeng, Yunlin; Faherty, Jacqueline et al. (26 November 2021). "Precise Masses and Orbits for Nine Radial-velocity Exoplanets". The Astronomical Journal 162 (6): 266. doi:10.3847/1538-3881/ac27ab. ISSN 0004-6256. Bibcode: 2021AJ....162..266L.
- ↑ 11.0 11.1 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. doi:10.1086/430500. ISSN 0067-0049. Bibcode: 2005ApJS..159..141V.
- ↑ 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. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HR+8935.
- ↑ Feng, Fabo et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series 262 (21): 21. doi:10.3847/1538-4365/ac7e57. Bibcode: 2022ApJS..262...21F.
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