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]
 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] |
| Distance | 136.7 ± 0.6 ly (41.9 ± 0.2 pc) |
| Absolute magnitude (MV) | +0.62[5] |
| Details | |
| Mass | 2.01[6] M☉ |
| Radius | 9.94±0.09[7] R☉ |
| Luminosity | 57.2±2.1[7] L☉ |
| Surface gravity (log g) | 2.87±0.09[8] cgs |
| Temperature | 5,032±48[7] K |
| Metallicity [Fe/H] | +0.09±0.04[8] dex |
| Rotation | 67[9] d |
| Rotational velocity (v sin i) | 2.8[4] km/s |
| Age | 2.48[6] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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
editIn 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
editOne 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
edit- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ "ksi Her". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-04-08.
{{cite web}}: CS1 maint: postscript (link) - ^ 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.
- ^ 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.
- ^ "/ftp/cats/more/HIP/cdroms/cats". Centre de Données astronomiques de Strasbourg. Strasbourg astronomical Data Center. Retrieved 15 October 2022.
- ^ "ksi Her". The International Variable Star Index. AAVSO. Retrieved 3 December 2022.
- ^ Allen, R. H. (1963), Star Names, Their Lore and Meaning, Dover, p. 246, retrieved 2017-04-11.
- ^ (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