Xi Herculis is a solitary[1] 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.[3] 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.[4]

This is an evolved G-type giant star with a stellar classification of G8 III.[5] 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 3.03e30 erg s−1 in the 0.3–10 keV band.[6] It has twice[7] the mass of the Sun but, at the age of two and a half billion years,[7] 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.[8]

Xi Herculis was discovered to be a variable star when the Hipparcos data was analyzed.[9] It is a semiregular variable star, oscillating in brightness by 3 hundredths of a magnitude, over a period of 120.8 days.[10]

Chinese name

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"),[11] but in Chinese literature, that name is applied to ο Her.[12]

Markov 1, the mini teapot

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.[citation needed]

References

  1. ^ 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
  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 ^ Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M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. ^
  4. ^ 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
  5. ^ 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
  6. ^ 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
  7. ^ 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
  8. ^ 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
  9. ^ Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V.; Frolov, M. S.; Antipin, S. V.; Kireeva, N. N.; Pastukhova, E. N. (January 1999). "The 74th Special Name-list of Variable Stars". Information Bulletin on Variable Stars. 4659. Bibcode:1999IBVS.4659....1K. Retrieved 23 December 2024.
  10. ^ "ksi Her". The International Variable Star Index. AAVSO. Retrieved 3 December 2022.
  11. ^ Allen, R. H. (1963), "Star Names, Their Lore and Meaning", Dover, p. 246, retrieved 2017-04-11
  12. ^ (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