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Xi Herculis

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Xi Herculis

ξ Herculis in optical light
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hercules
Right ascension 17h 57m 45.88567s[1]
Declination +29° 14′ 52.3660″[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: 81.919 mas/yr[1]
Dec.: −18.962 mas/yr[1]
Parallax (π)23.8544 ± 0.1068 mas[1]
Distance136.7 ± 0.6 ly
(41.9 ± 0.2 pc)
Absolute magnitude (MV)+0.62[5]
Details
Mass2.01[6] M☉
Radius9.94±0.09[7] R☉
Luminosity57.2±2.1[7] L☉
Surface gravity (log g)2.87±0.09[8] cgs
Temperature5,032±48[7] K
Metallicity [Fe/H]+0.09±0.04[8] dex
Rotation67[9] d
Rotational velocity (v sin i)2.8[4] km/s
Age2.48[6] Gyr
Other designations
ξ Her, 92 Her, BD+29° 3156, HD 163993, HIP 87933, HR 6703, SAO 85590[10]
Database references
SIMBADdata

Xi Herculis is a solitary[11] 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 23.85 mas as seen from Earth, it is located 137 light years from the Sun.[1] 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.[12]

A light curve for Xi Herculis, plotted from Hipparcos data[13]

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.[9] 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 times the Sun's radius. The star is radiating 57 times the solar luminosity from its photosphere at an effective temperature of 5,032 K.[7]

Xi Herculis is a semiregular variable star, oscillating in brightness by 3 hundredths of a magnitude, over a period of 120.8 days.[14]

Chinese name

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In R.H.Allen's book Star Names: Their Lore and Meaning, this star, together with ν Her and 99 Her (b Herculis) represent the state of Zhongshan (or Chung Shan' "the Middle Mountain"),[15] but in Chinese literature, that names is applied to ο Her.[16]

Markov 1, the mini teapot

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One third of a degree to the north-northwest of Xi Herculis is the location of a telescopic asterism in the shape of a teapot. This teapot (Markov 1) could be seen as a somewhat twisted small equivalent of the large and easy to recognize teapot asterism in the constellation Sagittarius.

References

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  1. ^ a b c d e 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. ^ 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 (1): 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333.
  4. ^ a b 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, S2CID 121883397.
  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:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114, 88.
  7. ^ a b c d Baines, Ellyn K.; Thomas Armstrong, J.; Clark, James H.; Gorney, Jim; Hutter, Donald J.; Jorgensen, Anders M.; Kyte, Casey; Mozurkewich, David; Nisley, Ishara; Sanborn, Jason; Schmitt, Henrique R.; Van Belle, Gerard T. (2021). "Angular Diameters and Fundamental Parameters of Forty-four Stars from the Navy Precision Optical Interferometer". The Astronomical Journal. 162 (5): 198. arXiv:2211.09030. Bibcode:2021AJ....162..198B. doi:10.3847/1538-3881/ac2431.
  8. ^ a b Prugniel, Ph.; et al. (July 2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: A165, arXiv:1104.4952, Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769, S2CID 54940439.
  9. ^ 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.
  10. ^ "ksi Her". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-04-08.{{cite web}}: CS1 maint: postscript (link)
  11. ^ 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:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  12. ^ 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/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304.
  13. ^ "/ftp/cats/more/HIP/cdroms/cats". Centre de Données astronomiques de Strasbourg. Strasbourg astronomical Data Center. Retrieved 15 October 2022.
  14. ^ "ksi Her". The International Variable Star Index. AAVSO. Retrieved 3 December 2022.
  15. ^ Allen, R. H. (1963), Star Names, Their Lore and Meaning, Dover, p. 246, retrieved 2017-04-11.
  16. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 6 日 Archived 2021-05-15 at the Wayback Machine
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