# HD 128311

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Star in the constellation Boötes

HD 128311 A near infrared (Y band) light curve for HN Boötes, adapted from Strassmeier et al. (2000)[1] Observation data Epoch J2000 Equinox J2000 Constellation Boötes Right ascension 14h 36m 00.56073s[2] Declination +09° 44′ 47.4536″[2] Apparent magnitude (V) 7.48[3] Characteristics Spectral type K3V[4] B−V color index 0.973±0.004[3] Variable type BY Dra[5] Astrometry Radial velocity (Rv) −9.62±0.15[2] km/s Proper motion (μ) RA: 204.360[2] mas/yr Dec.: −250.390[2] mas/yr Parallax (π) 61.2111±0.0740 mas[2] Distance 53.28 ± 0.06 ly (16.34 ± 0.02 pc) Absolute magnitude (MV) 6.39[3] Details Mass 0.82[6] M☉ Radius 0.78±0.01[2] R☉ Luminosity 0.308±0.001[2] L☉ Surface gravity (log g) 4.58[6] cgs Temperature 4,863+46 −15[2] K Metallicity [Fe/H] 0.08[7] dex 0.12[6] dex Rotational velocity (v sin i) 5.6[6] km/s Age 0.5–1.0 Gyr[8] 6.35[6] Gyr Other designations HN Boo, BD+10°2710, GC 19679, GJ 3860, HD 128311, HIP 71395, SAO 120554, LTT 14312, GSC 00910-00165[9] Database references SIMBAD data ARICNS data

**HD 128311** is a [variable star](/source/Variable_star) in the northern [constellation](/source/Constellation) of [Boötes](/source/Bo%C3%B6tes). It has the [variable star designation](/source/Variable_star_designation) **HN Boötis**, while HD 128311 is the star's designation in the *[Henry Draper Catalogue](/source/Henry_Draper_Catalogue)*. The star is invisible to the [naked eye](/source/Naked_eye) with an [apparent visual magnitude](/source/Apparent_visual_magnitude) that fluctuates around 7.48.[3] It is located at a distance of 53 [light years](/source/Light_year) from the [Sun](/source/Sun) based on [parallax](/source/Stellar_parallax), but is drifting closer with a [radial velocity](/source/Radial_velocity) of −9.6 km/s.[2] Two confirmed [extrasolar planets](/source/Extrasolar_planet) have been detected in orbit around this star.[8]

The [stellar classification](/source/Stellar_classification) of HN Boo is K3V,[4] which indicates this is a [K-type main sequence star](/source/K-type_main_sequence_star). Klaus G. Strassmeier *et al.* announced that the star's brightness varies, in the year 2000.[1] It was given its variable star designation in 2006.[10] It is a [BY Draconis-type variable](/source/BY_Draconis_variable), randomly varying in brightness by 0.04 in magnitude over a period of 11.54 days[5] due to [star spots](/source/Star_spot) and high [chromospheric activity](/source/Chromospheric_activity). The star exhibits strong emission, which suggests an age of 0.5–1.0 billion years.[8] It has 82% of the [mass of the Sun](/source/Mass_of_the_Sun) and 78% of the [Sun's radius](/source/Sun's_radius). The [metallicity](/source/Metallicity) of the star, meaning its abundance of heavier elements, appears slightly higher than in the Sun. It is radiating 31% of the [luminosity of the Sun](/source/Luminosity_of_the_Sun) from its [photosphere](/source/Photosphere) at an [effective temperature](/source/Effective_temperature) of 4,863 K.[6]

## Planetary system

The HD 128311 planetary system Companion (in order from star) Mass Semimajor axis (AU) Orbital period (days) Eccentricity Inclination (°) Radius d (unconfirmed) ≥0.133±0.005[11] MJ 0.092±0.004[11] 11.2210±0.0008[11] 0.196±0.030[11] — — b 1.9+0.7 −0.3[12] MJ 1.09±0.01[12] 453.019±0.404[11] 0.30±0.04[12] 90+30 −40[12] — c 3.4+0.6 −0.2[12] MJ 1.75±0.02[12] 921.538±1.15[11] 0.19+0.05 −0.07[12] 70+40 −20[12] —

In 2002, the discovery of the [exoplanet](/source/Exoplanet) [HD 128311 b](/source/HD_128311_b) was announced by [Paul Butler](/source/R._Paul_Butler).[13] In 2005, the discovery of a second exoplanet [HD 128311 c](/source/HD_128311_c) was announced by [Steve Vogt](/source/Steven_S._Vogt).[8]

Most likely, the system has been formed in a very turbulent disc.[7] The authors were able to show with both analytic and numerical models that certain libration modes are readily excited by turbulence. It was initially thought that the system could have been resulted from planet–planet scattering, but this is rather unlikely.

In 2014, the true mass of HD 128311 c was measured via [astrometry](/source/Astrometry). The same study also proposed a third planetary candidate, but it has not been confirmed.[11] In 2026, the mass of HD 128311 b was also measured with astrometry.[12]

Time evolution of orbital elements in the system HD128311. This left panel in this plot shows the most likely formation scenario for the planetary system. The right panel shows the observed orbital configuration.

## References

1. ^ [***a***](#cite_ref-Strassmeier_1-0) [***b***](#cite_ref-Strassmeier_1-1) Strassmeier, K. G.; Washuettl, A.; Granzer, Th.; Scheck, M.; Weber, M. (March 2000). ["The Vienna-KPNO search for Doppler-imaging candidate stars"](https://doi.org/10.1051%2Faas%3A2000328). *Astronomy & Astrophysics Supplement Series*. **142** (2): 275–311. [Bibcode](/source/Bibcode_(identifier)):[2000A&AS..142..275S](https://ui.adsabs.harvard.edu/abs/2000A&AS..142..275S). [doi](/source/Doi_(identifier)):[10.1051/aas:2000328](https://doi.org/10.1051%2Faas%3A2000328).

1. ^ [***a***](#cite_ref-GaiaDR2_2-0) [***b***](#cite_ref-GaiaDR2_2-1) [***c***](#cite_ref-GaiaDR2_2-2) [***d***](#cite_ref-GaiaDR2_2-3) [***e***](#cite_ref-GaiaDR2_2-4) [***f***](#cite_ref-GaiaDR2_2-5) [***g***](#cite_ref-GaiaDR2_2-6) [***h***](#cite_ref-GaiaDR2_2-7) [***i***](#cite_ref-GaiaDR2_2-8) [***j***](#cite_ref-GaiaDR2_2-9) [Brown, A. G. A.](/source/Anthony_Brown_(scientist)); et al. ([Gaia collaboration](/source/Data_Processing_and_Analysis_Consortium)) (August 2018). ["*Gaia* Data Release 2: Summary of the contents and survey properties"](https://doi.org/10.1051%2F0004-6361%2F201833051). *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. **616**. A1. [arXiv](/source/ArXiv_(identifier)):[1804.09365](https://arxiv.org/abs/1804.09365). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A...1G](https://ui.adsabs.harvard.edu/abs/2018A&A...616A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201833051](https://doi.org/10.1051%2F0004-6361%2F201833051). [Gaia DR2 record for this source](https://vizier.u-strasbg.fr/viz-bin/VizieR-S?Gaia%20DR2%201176209886733406592) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Anderson_Francis_2012_3-0) [***b***](#cite_ref-Anderson_Francis_2012_3-1) [***c***](#cite_ref-Anderson_Francis_2012_3-2) [***d***](#cite_ref-Anderson_Francis_2012_3-3) Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". *Astronomy Letters*. **38** (5): 331. [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971). [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A). [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015). [S2CID](/source/S2CID_(identifier)) [119257644](https://api.semanticscholar.org/CorpusID:119257644).

1. ^ [***a***](#cite_ref-Koen_et_al_2010_4-0) [***b***](#cite_ref-Koen_et_al_2010_4-1) Koen, C.; et al. (April 21, 2010). ["UBV(RI)CJHK observations of Hipparcos-selected nearby stars"](https://doi.org/10.1111%2Fj.1365-2966.2009.16182.x). *Monthly Notices of the Royal Astronomical Society*. **403** (4): 1949–1968. [Bibcode](/source/Bibcode_(identifier)):[2010MNRAS.403.1949K](https://ui.adsabs.harvard.edu/abs/2010MNRAS.403.1949K). [doi](/source/Doi_(identifier)):[10.1111/j.1365-2966.2009.16182.x](https://doi.org/10.1111%2Fj.1365-2966.2009.16182.x).

1. ^ [***a***](#cite_ref-gcvs_5-0) [***b***](#cite_ref-gcvs_5-1) Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". *Astronomy Reports*. **61** (1): 80. [Bibcode](/source/Bibcode_(identifier)):[2017ARep...61...80S](https://ui.adsabs.harvard.edu/abs/2017ARep...61...80S). [doi](/source/Doi_(identifier)):[10.1134/S1063772917010085](https://doi.org/10.1134%2FS1063772917010085). [S2CID](/source/S2CID_(identifier)) [125853869](https://api.semanticscholar.org/CorpusID:125853869).

1. ^ [***a***](#cite_ref-Luck2017_6-0) [***b***](#cite_ref-Luck2017_6-1) [***c***](#cite_ref-Luck2017_6-2) [***d***](#cite_ref-Luck2017_6-3) [***e***](#cite_ref-Luck2017_6-4) [***f***](#cite_ref-Luck2017_6-5) Luck, R. Earle (January 2017). ["Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants"](https://doi.org/10.3847%2F1538-3881%2F153%2F1%2F21). *The Astronomical Journal*. **153** (1): 19. [arXiv](/source/ArXiv_(identifier)):[1611.02897](https://arxiv.org/abs/1611.02897). [Bibcode](/source/Bibcode_(identifier)):[2017AJ....153...21L](https://ui.adsabs.harvard.edu/abs/2017AJ....153...21L). [doi](/source/Doi_(identifier)):[10.3847/1538-3881/153/1/21](https://doi.org/10.3847%2F1538-3881%2F153%2F1%2F21). [S2CID](/source/S2CID_(identifier)) [119511744](https://api.semanticscholar.org/CorpusID:119511744). 21.

1. ^ [***a***](#cite_ref-Rein2009_7-0) [***b***](#cite_ref-Rein2009_7-1) Rein, Hanno; Papaloizou, J. C. B. (2009). "On the evolution of mean motion resonances through stochastic forcing: Fast and slow libration modes and the origin of HD128311". *Astronomy and Astrophysics*. **497** (2): 595–609. [arXiv](/source/ArXiv_(identifier)):[0811.1813](https://arxiv.org/abs/0811.1813). [Bibcode](/source/Bibcode_(identifier)):[2009A&A...497..595R](https://ui.adsabs.harvard.edu/abs/2009A&A...497..595R). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/200811330](https://doi.org/10.1051%2F0004-6361%2F200811330). [S2CID](/source/S2CID_(identifier)) [12286814](https://api.semanticscholar.org/CorpusID:12286814).

1. ^ [***a***](#cite_ref-Vogt2005_8-0) [***b***](#cite_ref-Vogt2005_8-1) [***c***](#cite_ref-Vogt2005_8-2) [***d***](#cite_ref-Vogt2005_8-3) Vogt, Steven S.; et al. (2005). ["Five New Multicomponent Planetary Systems"](https://authors.library.caltech.edu/36250/1/0004-637X_632_1_638.pdf) (PDF). *The Astrophysical Journal*. **632** (1): 638–658. [Bibcode](/source/Bibcode_(identifier)):[2005ApJ...632..638V](https://ui.adsabs.harvard.edu/abs/2005ApJ...632..638V). [doi](/source/Doi_(identifier)):[10.1086/432901](https://doi.org/10.1086%2F432901). [S2CID](/source/S2CID_(identifier)) [16509245](https://api.semanticscholar.org/CorpusID:16509245).

1. **[^](#cite_ref-SIMBAD_9-0)** ["HD 128311"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+128311). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2021-04-06.

1. **[^](#cite_ref-Kazarovets2006_10-0)** Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (August 2006). ["The 78th Name-List of Variable Stars"](https://ibvs.konkoly.hu/pub/ibvs/5701/5721.pdf) (PDF). *Information Bulletin on Variable Stars*. **5721**: 1–45. [Bibcode](/source/Bibcode_(identifier)):[2006IBVS.5721....1K](https://ui.adsabs.harvard.edu/abs/2006IBVS.5721....1K). Retrieved 6 December 2024.

1. ^ [***a***](#cite_ref-McArthur2014_11-0) [***b***](#cite_ref-McArthur2014_11-1) [***c***](#cite_ref-McArthur2014_11-2) [***d***](#cite_ref-McArthur2014_11-3) [***e***](#cite_ref-McArthur2014_11-4) [***f***](#cite_ref-McArthur2014_11-5) [***g***](#cite_ref-McArthur2014_11-6) McArthur, Barbara E.; et al. (2014). ["Astrometry, Radial Velocity, and Photometry: The HD 128311 System Remixed with Data from HST, HET, and APT"](https://doi.org/10.1088%2F0004-637X%2F795%2F1%2F41). *[The Astrophysical Journal](/source/The_Astrophysical_Journal)*. **795** (1): 41. [Bibcode](/source/Bibcode_(identifier)):[2014ApJ...795...41M](https://ui.adsabs.harvard.edu/abs/2014ApJ...795...41M). [doi](/source/Doi_(identifier)):[10.1088/0004-637X/795/1/41](https://doi.org/10.1088%2F0004-637X%2F795%2F1%2F41). [hdl](/source/Hdl_(identifier)):[2152/35199](https://hdl.handle.net/2152%2F35199). [S2CID](/source/S2CID_(identifier)) [122980723](https://api.semanticscholar.org/CorpusID:122980723).

1. ^ [***a***](#cite_ref-Van_Zandt_2026_12-0) [***b***](#cite_ref-Van_Zandt_2026_12-1) [***c***](#cite_ref-Van_Zandt_2026_12-2) [***d***](#cite_ref-Van_Zandt_2026_12-3) [***e***](#cite_ref-Van_Zandt_2026_12-4) [***f***](#cite_ref-Van_Zandt_2026_12-5) [***g***](#cite_ref-Van_Zandt_2026_12-6) [***h***](#cite_ref-Van_Zandt_2026_12-7) [***i***](#cite_ref-Van_Zandt_2026_12-8) Van Zandt, Judah; Gilbert, Gregory J.; Petigura, Erik A.; Giacalone, Steven; Howard, Andrew W.; Handley, Luke B. (2026-04-02). ["A Smooth Transition from Giant Planets to Brown Dwarfs from the Radial Occurrence Distribution"](https://doi.org/10.3847%2F1538-3881%2Fae5102). *The Astronomical Journal*. **171** (5): 267. [doi](/source/Doi_(identifier)):[10.3847/1538-3881/ae5102](https://doi.org/10.3847%2F1538-3881%2Fae5102). [ISSN](/source/ISSN_(identifier)) [0004-6256](https://search.worldcat.org/issn/0004-6256).

1. **[^](#cite_ref-Butler2003_13-0)** Butler, R. Paul; et al. (2003). "Seven New Keck Planets Orbiting G and K Dwarfs". *The Astrophysical Journal*. **582** (1): 455–466. [Bibcode](/source/Bibcode_(identifier)):[2003ApJ...582..455B](https://ui.adsabs.harvard.edu/abs/2003ApJ...582..455B). [CiteSeerX](/source/CiteSeerX_(identifier)) [10.1.1.7.6988](https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.7.6988). [doi](/source/Doi_(identifier)):[10.1086/344570](https://doi.org/10.1086%2F344570). [S2CID](/source/S2CID_(identifier)) [17608922](https://api.semanticscholar.org/CorpusID:17608922).

## External links

- ["Notes for star HD 128311"](https://web.archive.org/web/20070702185725/http://exoplanet.eu/star.php?st=HD+128311). *[Extrasolar Planets Encyclopaedia](/source/Extrasolar_Planets_Encyclopaedia)*. Archived from [the original](http://exoplanet.eu/star.php?st=HD+128311) on July 2, 2007. Retrieved 2008-08-18.

## External links

- [GJ 3860](http://webviz.u-strasbg.fr/viz-bin/VizieR-S?GJ%203860)

- [Extrasolar Planet Interactions](http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/) [Archived](https://web.archive.org/web/20160505160348/http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/) 2016-05-05 at the [Wayback Machine](/source/Wayback_Machine) by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona

- [Image HD 128311](http://aladin.u-strasbg.fr/AladinPreview?-c=14+36+00.5607%2B09+44+47.466&ident=V*+HN+Boo&submit=Aladin+previewer)

v t e HD 128311 System Stars HD 128311 Planets HD 128311 b HD 128311 c

v t e Constellation of Boötes Boötes in Chinese astronomy Boötes Void List of stars in Boötes Stars Bayer α (Arcturus) β (Nekkar) γ (Seginus) δ (Qigong) ε (Izar, Pulcherrima) ζ η (Muphrid) θ ι κ λ (Xuange) μ1 (Alkalurops) μ2 ν1 ν2 ξ ο π ρ (Kalasungsang) σ (Genghe) τ (Tepiamenit) υ φ χ ψ ω Flamsteed 1 2 3 6 (e) 7 9 10 11 12 (d) 13 14 15 18 20 22 (f) 24 (g) 26 31 32 33 34 (Alrumh) 38 (Merga) 39 40 44 (Quadrans) 45 (c) 46 (b) 47 (k) 50 Variable R S T RX ZZ AB BL BP BX BY CE CH CI CN CP CR CX CY (101 Vir) DE EK HN HP HD 118508 118889 122563 125040 125351 (A) 125658 126128 126129 126141 126200 126271 127304 127334 127726 128093 128198 129132 129357 130084 130603 130917 131040 131473 131496 (Arcalís) 132029 132406 132563 134064 134335 135438 135530 135944 141399 Other 2MASS J15031961+2525196 CFBDSIR 1458+10 Gliese 526 HAT-P-4 LHS 2924 PSR J1544+4937 SDSS J1416+1348 SDSS J1433+1011 TVLM 513-46546 WASP-14 WD 1425+540 ZTF J153932.16+502738.8 Exoplanets HAT-P-4b HD 128311 b c HD 132406 b HD 136418 b (Awasis) τ Boötis b TOI-1853 b WASP-14b Star clusters NGC 5466 Galaxies NGC 5008 5248 5251 5416 5490 5500 5504 5508 5514 5523 5529 5532 5533 5535 5539 5541 5544 5545 5548 5557 5559 5562 5579 5582 5591 5601 5603 5609 5613 5614 5615 5624 5629 5630 5641 5642 5653 5665 5676 5681 5682 5683 5698 5714 5722 5752 5753 5754 5755 5772 5778 5784 5790 5820 5821 5829 5837 5857 5875 5876 5886 5888 5896 5929 5930 5966 Numbered I II III Other 3C 295 3C 299 3C 300 3C 303 3C 315 4C 19.44 4C +26.42 7C 1354+2552 Abell 2009 BCG Arp 302 B2 1420+32 B2 1441+26 CEERS-2112 CEERS-93316 CEERS2-588 CLASS B1359+154 Cloverleaf quasar DDO 190 EGS-zs8-1 EGS-z11-R0 EGSY8p7 H1426+428 IC 4397 IC 4461 IC 4462 IC 4481 IC 4516 IRAS 13349+2438 IRAS 14394+5332 IRAS 15206+3342 LEDA 2108986 MACS 1423-z7p64 MACS J1447.4+0827 BCG Maisie's Galaxy Markarian 463 Markarian 471 Markarian 478 MS 1455.0+2232 BCG MS 1512-cB58 NVSS J141343+433945 OQ 172 OQ 530 PG 1411+442 PG 1543+489 PGC 93125 PGC 1470080 PKS 1345+125 PKS 1413+135 QSO B1422+202 RBS 1467 RGZ J145001.5+144747 RGZ J145039.8+441829 SBS 1415+437 SDSS J135646.10+102609.0 SDSS J1430+2303 Teacup galaxy UGC 8669 UGC 9128 UGC 9425 UGC 9684 UGC 9796 ULAS J1342+0928 VV 191 Galaxy clusters Abell 1795 Abell 1991 BoRG-58 IDCS J1426.5+3508 Astronomical events GRB 990123 GRB 080319B SCP 06F6 SN 2003fg SN 2005bc SN 2020tlf Category

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Adapted from the Wikipedia article [HD 128311](https://en.wikipedia.org/wiki/HD_128311) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/HD_128311?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.