HD 128311

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

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]
Distance53.28 ± 0.06 ly
(16.34 ± 0.02 pc)
Absolute magnitude (MV)6.39[3]
Details[6]
Mass0.82 M☉
Radius0.78±0.01[2] R☉
Luminosity0.308±0.001[2] L☉
Surface gravity (log g)4.58 cgs
Temperature4,863+46
−15[2] K
Metallicity [Fe/H]0.08[7] dex
0.12[6] dex
Rotational velocity (v sin i)5.6 km/s
Age0.5–1.0 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
SIMBADdata
ARICNSdata

The stellar classification of HN Boo is K3V,[4] which indicates this is a K-type main sequence star. It is a BY Draconis-type variable, randomly varying in brightness by 0.04 in magnitude over a period of 11.54 days[5] due to star spots and high 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 and 78% of the Sun's radius. The 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 from its photosphere at an effective temperature of 4,863 K.[6]

Planetary system

In 2002, the discovery of the exoplanet HD 128311 b was announced by Paul Butler.[10] In 2005, the discovery of a second exoplanet HD 128311 c was announced by Steve 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.

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.
The HD 128311 planetary system[8]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b >2.18 ± 0.22 MJ 1.099 ± 0.04 458.6 ± 6.8 0.25 ± 0.10 — —
c >3.21 ± 0.30 MJ 1.76 ± 0.13 928.3 ± 18 0.17 ± 0.09 — —

See also

References
  1. Strassmeier, K. G.; Washuettl, A.; Granzer, Th.; Scheck, M.; Weber, M. (March 2000). "The Vienna-KPNO search for Doppler-imaging candidate stars". Astronomy & Astrophysics Supplement Series. 142: 275–311. doi:10.1051/aas:2000328. Retrieved 6 November 2021.
  2. 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.
  3. 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.
  4. Koen, C.; et al. (April 21, 2010). "UBV(RI)CJHK observations of Hipparcos-selected nearby stars". Monthly Notices of the Royal Astronomical Society. 403 (4): 1949–1968. Bibcode:2010MNRAS.403.1949K. doi:10.1111/j.1365-2966.2009.16182.x.
  5. 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:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
  6. Luck, R. Earle (January 2017). "Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants". The Astronomical Journal. 153 (1): 19. arXiv:1611.02897. Bibcode:2017AJ....153...21L. doi:10.3847/1538-3881/153/1/21. S2CID 119511744. 21.
  7. 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:0811.1813. Bibcode:2009A&A...497..595R. doi:10.1051/0004-6361/200811330. S2CID 12286814.
  8. Vogt, Steven S.; et al. (2005). "Five New Multicomponent Planetary Systems" (PDF). The Astrophysical Journal. 632 (1): 638–658. Bibcode:2005ApJ...632..638V. doi:10.1086/432901.
  9. "HD 128311". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-04-06.
  10. Butler, R. Paul; et al. (2003). "Seven New Keck Planets Orbiting G and K Dwarfs". The Astrophysical Journal. 582 (1): 455–466. Bibcode:2003ApJ...582..455B. CiteSeerX 10.1.1.7.6988. doi:10.1086/344570.

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