NGC 6934

NGC 6934 (also known as Caldwell 47) is a globular cluster of stars in the northern constellation of Delphinus, about 52 kilolight-years distant from the Sun.[3] It was discovered by the German-born astronomer William Herschel on 24 September 1785.[4] The cluster is following a highly eccentric orbit (with an eccentricity of 0.81) through the Milky Way along an orbital plane that is inclined by 73° to the galactic plane. It may share a common dynamic origin with NGC 5466.[6] As of 2018, it has been poorly studied.[9]

NGC 6934
NGC 6934 by Hubble Space Telescope; 3.5′ view
Observation data (J2000 epoch)
ClassVIII[1]
ConstellationDelphinus
Right ascension20h 34m 11.37s[2]
Declination+07° 24′ 16.1″[2]
Distance52 kly (16 kpc)[3]
Apparent magnitude (V)8.83[4]
Apparent dimensions (V)1.20′[5]
Physical characteristics
Absolute magnitude−7.65[6]
Mass2.95×105[7] M☉
Metallicity = –1.47[7] dex
Other designationsCaldwell 47, NGC 6934[8]

This appears to be a Oosterhoff type I cluster with an intermediate metallicity.[10] It has an Shapley–Sawyer Concentration Class of VIII,[1] with a core radius of 15″[3] and a half-light radius of 36″.[5] The estimated mass is 295,000 times the mass of the Sun.[7] The cluster displays photometric anomalies, with a split subgiant branch on the HR diagram.[9] Searches for variable stars have discovered 85 in the cluster field, of which 79 are of the RR Lyrae class and one is a SX Phe variable.[10] There is some evidence for a tidal tail.[11]

References
  1. Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin, 849 (849): 11–14, Bibcode:1927BHarO.849...11S.
  2. Goldsbury, Ryan; et al. (December 2010). "The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters". The Astronomical Journal. 140 (6): 1830–1837. arXiv:1008.2755. Bibcode:2010AJ....140.1830G. doi:10.1088/0004-6256/140/6/1830. S2CID 119183070.
  3. Hessels, J. W. T.; et al. (November 2007), "A 1.4 GHz Arecibo Survey for Pulsars in Globular Clusters", The Astrophysical Journal, 670 (1): 363–378, arXiv:0707.1602, Bibcode:2007ApJ...670..363H, doi:10.1086/521780, S2CID 16914232.
  4. NGC 6934, SEDS, retrieved 2010-10-09
  5. Forbes, Duncan A.; et al. (October 2008). "Uniting old stellar systems: from globular clusters to giant ellipticals". Monthly Notices of the Royal Astronomical Society. 389 (4): 1924–1936. arXiv:0806.1090. Bibcode:2008MNRAS.389.1924F. doi:10.1111/j.1365-2966.2008.13739.x. S2CID 14108457.
  6. Dinescu, Dana I.; et al. (October 2001). "Orbits of Globular Clusters in the Outer Galaxy: NGC 7006". The Astronomical Journal. 122 (4): 1916–1927. arXiv:astro-ph/0106259. Bibcode:2001AJ....122.1916D. doi:10.1086/323094. S2CID 1232455.
  7. Boyles, J.; et al. (November 2011), "Young Radio Pulsars in Galactic Globular Clusters", The Astrophysical Journal, 742 (1): 51, arXiv:1108.4402, Bibcode:2011ApJ...742...51B, doi:10.1088/0004-637X/742/1/51, S2CID 118649860.
  8. "NGC 6934". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-10-08.
  9. Marino, A. F.; et al. (June 2018). "Metallicity Variations in the Type II Globular Cluster NGC 6934". The Astrophysical Journal. 859 (2): 20. arXiv:1804.04158. Bibcode:2018ApJ...859...81M. doi:10.3847/1538-4357/aabdea. S2CID 119461759. 81.
  10. Kaluzny, J.; et al. (March 2001). "Image-Subtraction Photometry of Variable Stars in the Field of the Globular Cluster NGC 6934". The Astronomical Journal. 121 (3): 1533–1550. arXiv:astro-ph/0010303. Bibcode:2001AJ....121.1533K. doi:10.1086/319411. S2CID 14431121.
  11. Wilhelm, R.; et al. (December 2002). "Does NGC 6934 Have a Tidal Tail?". Bulletin of the American Astronomical Society. 34: 1101. Bibcode:2002AAS...201.0702W.
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