Chi Herculis

Chi Herculis, Latinized from χ Herculis, is a Sun-like[12] star in the northern constellation of Hercules. Based upon an annual parallax shift of 63.16 mas as seen from Earth, it is located 51.6 light years from the Sun. The star is faintly visible to the naked eye with an apparent visual magnitude of 4.59.[2] It has a relatively high proper motion, showing a transverse movement of 0.769 arc seconds per year[13] and is drifting closer to the Sun with a radial velocity of −56 km/s.[4]

Not to be confused with X Herculis.
Chi Herculis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hercules
Right ascension 15h 52m 40.54114s[1]
Declination +42° 27′ 05.4511″[1]
Apparent magnitude (V) 4.59[2]
Characteristics
Spectral type G0V Fe-0.8 CH-0.5[3]
U−B color index +0.01[2]
B−V color index +0.57[2]
Astrometry
Radial velocity (Rv)−56.09±0.10[4] km/s
Proper motion (μ) RA: +438.816[1] mas/yr
Dec.: +630.313[1] mas/yr
Parallax (π)63.1627 ± 0.1490 mas[5]
Distance51.6 ± 0.1 ly
(15.83 ± 0.04 pc)
Absolute magnitude (MV)+3.59[6]
Orbit[7]
Period (P)51.2865±0.4082 d
Semi-major axis (a)0.96±0.58″
Eccentricity (e)0.0000
Inclination (i)131.68±27.61°
Longitude of the node (Ω)51.69±37.96°
Periastron epoch (T)48349.0039±4.4425
Argument of periastron (ω)
(secondary)		0.00°
Details
Mass1.054+0.015
−0.054[8] M☉
Radius1.71+0.04
−0.05[8] R☉
Luminosity3.24[6] L☉
Surface gravity (log g)4.02+0.02
−0.03[8] cgs
Temperature5,837[3] K
Metallicity [Fe/H]−0.45[3] dex
Rotational velocity (v sin i)2.4[9] km/s
Age7.4[10] Gyr
Other designations
χ Her, 1 Her, BD+42° 2648, FK5 1166, GJ 602, HD 142373, HIP 77760, HR 5914, SAO 45772, WDS J16254+1402AB[11]
Database references
SIMBADdata

This is a suspected binary star system for which orbital elements have been published, listing a circular orbit with period of 51.3 days.[7] However, sources do not confirm this and so the binarity remains in doubt.[14] The observable component is a G-type main sequence star with a stellar classification of G0V Fe-0.8 CH-0.5,[3] indicating abnormal deficiencies in iron and the CH molecule. The surface magnetic activity for this star is distinctly lower than the typical level for regular stars, and hence it is considered a good candidate for being in a Maunder minimum phase.[15]

Chi Herculis is an older star with an estimated age of 7.4 billion years and is spinning with a projected rotational velocity of 2.4.[9] It has a mass slightly higher than the Sun and 1.7 times the Sun's radius.[8] The star's photosphere is radiating 3.24[6] times the Sun's luminosity at an effective temperature of 5,837.[3] Chi Herculis has been examined for the presence of an infrared excess that could indicate an orbiting debris disk, but none was found.[12] The low metal content and a relatively high velocity of 80 kilometers per second suggest that the star is a visitor from another part of the Galaxy, and is just moving through the local neighborhood.[16]

References
  1. 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.
  2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
  3. Gray, R. O.; et al. (July 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, S2CID 119476992.
  4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
  5. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  6. 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.
  7. Hartkopf, W. I.; et al. (2006), Sixth Catalog of Orbits of Visual Binary Stars, archived from the original on 2011-05-17, retrieved 2017-04-03
  8. Takeda, Genya; et al. (February 2007), "Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog", The Astrophysical Journal Supplement Series, 168 (2): 297–318, arXiv:astro-ph/0607235, Bibcode:2007ApJS..168..297T, doi:10.1086/509763, S2CID 18775378.
  9. Fekel, F. C. (May 1997), "Rotational Velocities of Late-Type Stars", Publications of the Astronomical Society of the Pacific, 109: 514–523, Bibcode:1997PASP..109..514F, doi:10.1086/133908.
  10. Casagrande, L.; et al. (2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy & Astrophysics, 530 (A138): 21, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276, S2CID 56118016.
  11. "* chi Her". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-04-05.{{cite web}}: CS1 maint: postscript (link)
  12. Maldonado, J.; et al. (May 2012), "Metallicity of solar-type stars with debris discs and planets", Astronomy and Astrophysics, 541: A40, arXiv:1202.5884, Bibcode:2012A&A...541A..40M, doi:10.1051/0004-6361/201218800, S2CID 46328823.
  13. Lépine, Sébastien; Shara, Michael M. (March 2005), "A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)", The Astronomical Journal, 129 (3): 1483–1522, arXiv:astro-ph/0412070, Bibcode:2005AJ....129.1483L, doi:10.1086/427854, S2CID 2603568.
  14. Rodriguez, David R.; et al. (May 2015), "Stellar multiplicity and debris discs: an unbiased sample", Monthly Notices of the Royal Astronomical Society, 449 (3): 3160–3170, arXiv:1503.01320, Bibcode:2015MNRAS.449.3160R, doi:10.1093/mnras/stv483.
  15. Hempelmann, A.; et al. (February 1996), "Coronal X-ray emission of late-type MS stars in relation to chromospheric activity and magnetic cycles", International Conference on X-ray Astronomy and Astrophysics: Röntgenstrahlung from the Universe, pp. 45–46, Bibcode:1996rftu.proc...45H.
  16. Kaler, Jim. "Chi Herculis". stars.astro.illinois.edu.
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