Xi Herculis

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Xi Herculis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hercules
Right ascension 17h 57m 45.88571s[1]
Declination +29° 14′ 52.3675″[1]
Apparent magnitude (V) 3.70[2]
Characteristics
Spectral type G8 III[3]
U−B color index +0.66[2]
B−V color index +0.93[2]
Astrometry
Radial velocity (Rv) −1.65±0.17[4] km/s
Proper motion (μ) RA: +82.44[1] mas/yr
Dec.: −18.73[1] mas/yr
Parallax (π) 23.84 ± 0.15[1] mas
Distance 136.8 ± 0.9 ly
(41.9 ± 0.3 pc)
Absolute magnitude (MV) +0.62[5]
Details
Mass 2.01[6] M
Radius 10[4] R
Luminosity 51[4] L
Surface gravity (log g) 2.87±0.09[7] cgs
Temperature 4,966±15[4] K
Metallicity [Fe/H] +0.09±0.04[7] dex
Rotation 67[8] d
Rotational velocity (v sin i) 2.8[4] km/s
Age 2.48[6] Gyr
Other designations
ξ Her, 92 Her, BD+29° 3156, HD 163993, HIP 87933, HR 6703, SAO 85590[9]
Database references
SIMBAD data

Xi Herculis is a solitary[10] star located within the northern constellation of Hercules. The star is visible to the naked eye with an apparent visual magnitude of 3.70.[2] Based upon an annual parallax shift of 23.84 mas as seen from Earth, it is located 137 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.05 due to interstellar dust. It is a suspected member of the Sirius stream of co-moving stars.[11]

This is an evolved G-type giant star with a stellar classification of G8 III.[3] It is a red clump star, which means it is on the horizontal branch and generating energy through the thermonuclear fusion of hydrogen at its core. The star is emitting X-rays with a luminosity of 3.03×1030 erg s−1 in the 0.3–10 keV band.[8] It has twice[6] the mass of the Sun but, at the age of two and a half billion years,[6] it has expanded to 10[4] times the Sun's radius. The star is radiating 51[4] times the solar luminosity from its photosphere at an effective temperature of 4,966 K.[4]

Chinese name[edit]

In R.H.Allen's version, this star, together with ν Her and 99 Her (b Herculis) were represent states Zhongshan (or Chung Shan' "the Middle Mountain"),[12] but in Chinese literature, it was only for ο Her.[13][clarification needed]

References[edit]

  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d 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. ^ a b Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics, 11: 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333. 
  4. ^ a b c d e f g h Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209. 
  5. ^ Böhm-Vitense, Erika; et al. (December 2000), "Ultraviolet Emission Lines in BA and Non-BA Giants", The Astrophysical Journal, 545 (2): 992−999, Bibcode:2000ApJ...545..992B, doi:10.1086/317850. 
  6. ^ a b c d Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466Freely accessible, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, 88. 
  7. ^ a b Prugniel, Ph.; et al. (July 2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: A165, arXiv:1104.4952Freely accessible, Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769. 
  8. ^ a b Gondoin, P. (December 2005), "The relation between X-ray activity and rotation in intermediate-mass G giants", Astronomy and Astrophysics, 444 (2): 531−538, Bibcode:2005A&A...444..531G, doi:10.1051/0004-6361:20053567. 
  9. ^ "ksi Her -- Long-period variable star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-04-08. 
  10. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878Freely accessible, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x. 
  11. ^ Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579Freely accessible, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272. 
  12. ^ Allen, R. H. (1963), Star Names, Their Lore and Meaning, Dover, p. 246, retrieved 2017-04-11. 
  13. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 6 日