HD 154345

HD 154345 is a star in the northern constellation of Hercules. With an apparent visual magnitude of +6.76[2] it is a challenge to view with the naked eye, but using binoculars it is an easy target.[8] The distance to this star is 59.6 light years based on parallax, but it is drifting closer with a radial velocity of −47 km/s.[1] At least one exoplanet is orbiting this star.[9]

HD 154345
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hercules
Right ascension 17h 02m 36.40381s[1]
Declination +47° 04′ 54.7642″[1]
Apparent magnitude (V) +6.76[2]
Characteristics
Spectral type G8V[3]
U−B color index 0.27
B−V color index 0.728±0.005[2]
Astrometry
Radial velocity (Rv)−47.08±0.12[1] km/s
Proper motion (μ) RA: 123.274 mas/yr[1]
Dec.: 853.639 mas/yr[1]
Parallax (π)54.7359 ± 0.0176 mas[1]
Distance59.59 ± 0.02 ly
(18.270 ± 0.006 pc)
Absolute magnitude (MV)+5.41[2]
Details[4]
Mass0.90±0.01 M☉
Radius0.85±0.01 R☉
Luminosity0.620±0.002 L☉
Surface gravity (log g)4.53±0.01 cgs
Temperature5,557±15 K
Metallicity [Fe/H]−0.14±0.04[5] dex
Rotation27.8±1.7 d[6]
Age4.10±1.20 Gyr
Other designations
BD+47°2420, GC 23011, GJ 651, HD 154345, HIP 83389, SAO 46452, GCRV 9834[7]
Database references
SIMBADdata

The stellar classification of HD 154345 is G8V,[3] matching an ordinary G-type main-sequence star that is generating energy by core hydrogen fusion. The magnetic activity cycle of this star is curiously correlated with the radial velocity variations induced by its putative planetary companion.[10][11] It is around four[4] billion years old and is spinning with a rotation period of 28 days.[6] The star is smaller and less massive than the Sun. It is radiating 62% of the luminosity of the Sun from its photosphere at an effective temperature of 5,557 K.[4]

Planetary system

In 2006, a long-period, wide-orbiting planet was observed by radial velocity, and published in May 2007, gaining the designation HD 154345 b.[9] It has been called a "Jupiter twin".[12] While the existence of HD 154345 b has been unclear due to the correlation of its orbital period with the star's activity cycle,[10] a study in 2021 further confirmed its planetary nature.[13]

The complete observation of its nine-year orbit rules out any interior planets of minimum mass (m sini) greater than 0.3 Jupiter.[12] The star rotates at an inclination of 50+40
−26 degrees relative to Earth.[6] It is probable that the planet shares that inclination.[14][15] In 2023, the inclination and true mass of HD 154345 b were determined via astrometry, consistent within the margin of error with the stellar rotational inclination.[16]

The system's habitable zone stretches from 0.64 AU out to 1.26 AU, and is narrower than the Sun's. It forms a stable region where an Earth-mass exoplanet could orbit.[17]

The HD 154345 planetary system[16]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(years)		 Eccentricity Inclination Radius
b 1.19+0.14
−0.11 MJ		 4.2+0.14
−0.15		 9.15±0.11 0.157+0.03
−0.029		 69+13
−12 or 111+12
−13°		 —

References
  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. 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.
  3. Cowley, A. P.; et al. (1967). "Spectral classification and photometry of high proper motion stars". The Astronomical Journal. 72: 1334. Bibcode:1967AJ.....72.1334C. doi:10.1086/110413.
  4. Bonfanti, A.; Ortolani, S.; Nascimbeni, V. (2016). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics. 585: 14. arXiv:1511.01744. Bibcode:2016A&A...585A...5B. doi:10.1051/0004-6361/201527297. S2CID 53971692. A5.
  5. Aguilera-Gómez, Claudia; et al. (June 2018). "Lithium abundance patterns of late-F stars: an in-depth analysis of the lithium desert". Astronomy & Astrophysics. 614: 15. arXiv:1803.05922. Bibcode:2018A&A...614A..55A. doi:10.1051/0004-6361/201732209. S2CID 62799777. A55.
  6. Simpson, E. K.; et al. (November 2010). "Rotation periods of exoplanet host stars". Monthly Notices of the Royal Astronomical Society. 408 (3): 1666–1679. arXiv:1006.4121. Bibcode:2010MNRAS.408.1666S. doi:10.1111/j.1365-2966.2010.17230.x. S2CID 6708869.
  7. "HD 154345". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-01-19.
  8. "The astronomical magnitude scale". International Comet Quarterly. Retrieved 2021-01-19.
  9. Wright, J. T.; et al. (2007). "Four New Exoplanets and Hints of Additional Substellar Companions to Exoplanet Host Stars". The Astrophysical Journal. 657 (1): 533–545. arXiv:astro-ph/0611658. Bibcode:2007ApJ...657..533W. doi:10.1086/510553. S2CID 35682784.
  10. Wright, J. T. (October 2015). Boisse, I.; Demangeon, O.; Bouchy, F.; Arnold, L. (eds.). Twenty Years of Precise Radial Velocities at Keck and Lick Observatories. Proceedings of colloquium 'Twenty years of giant exoplanets' held at Observatoire de Haute Provence, France, October 5-9, 2015. Observatoire de Haute-Provence, Institut Pythéas. pp. 8–17. arXiv:1603.08384. Bibcode:2015tyge.conf....8W.
  11. Wright, Jason Thomas; Miller, Brendan (August 2015). Magnetism and Activity of Planet-Hosting Stars. IAU General Assembly, Meeting #29. arXiv:1706.07102. Bibcode:2015IAUGA..2258453W. 2258453.
  12. Wright, J. T.; et al. (2008). "The Jupiter Twin HD 154345b". The Astrophysical Journal Letters. 683 (1): L63–L66. arXiv:0802.1731. Bibcode:2008ApJ...683L..63W. doi:10.1086/587461. S2CID 16808434.
  13. Rosenthal, Lee J.; Fulton, Benjamin J.; Hirsch, Lea A.; Isaacson, Howard T.; Howard, Andrew W.; Dedrick, Cayla M.; Sherstyuk, Ilya A.; Blunt, Sarah C.; Petigura, Erik A.; Knutson, Heather A.; Behmard, Aida; Chontos, Ashley; Crepp, Justin R.; Crossfield, Ian J. M.; Dalba, Paul A.; Fischer, Debra A.; Henry, Gregory W.; Kane, Stephen R.; Kosiarek, Molly; Marcy, Geoffrey W.; Rubenzahl, Ryan A.; Weiss, Lauren M.; Wright, Jason T. (2021). "The California Legacy Survey. I. A Catalog of 178 Planets from Precision Radial Velocity Monitoring of 719 Nearby Stars over Three Decades". The Astrophysical Journal Supplement Series. 255: 8. arXiv:2105.11583. Bibcode:2021ApJS..255....8R. doi:10.3847/1538-4365/abe23c. S2CID 235186973.
  14. "hd_154345_b". Extrasolar Planet Encyclopaedia. Retrieved November 12, 2012.
  15. Sanchis-Ojeda, Roberto; Winn, Josh N.; Fabrycky, Daniel C. (2012). "Starspots and spin-orbit alignment for Kepler cool host stars". Astronomische Nachrichten. 334 (1–2): 180–183. arXiv:1211.2002. Bibcode:2013AN....334..180S. doi:10.1002/asna.201211765. S2CID 38743202.
  16. Xiao, Guang-Yao; Liu, Yu-Juan; et al. (March 2023). "The Masses of a Sample of Radial-Velocity Exoplanets with Astrometric Measurements". Research in Astronomy and Astrophysics. arXiv:2303.12409.
  17. Funk, B.; Libert, A. -S.; Süli, Á.; Pilat-Lohinger, E. (February 2011). "On the influence of the Kozai mechanism in habitable zones of extrasolar planetary systems". Astronomy and Astrophysics. 526: 7. Bibcode:2011A&A...526A..98F. doi:10.1051/0004-6361/201015218. A98.
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