NGC 2506

NGC 2506 (also known as Caldwell 54) is a mildly-elongated[6] open cluster of stars in the equatorial constellation of Monoceros, located at a distance of 12.7 kly[2] from the Sun near the Galactic anti-center.[4] It was discovered by William Herschel in 1791.[7] The cluster lies around 10,000 ly from the Galactic Center and about 1,600 ly above the Galactic plane.[4] It is of intermediate age,[2] estimated at around two billion years.[2] The cluster has an angular radius of 12′ and a core radius of 4.8′.[8]

NGC 2506
An image of NGC 2506
Observation data (J2000 epoch)
ConstellationMonoceros
Right ascension08h 00m 01.0s[1]
Declination−10° 46′ 12″[1]
Distance12.7 ± 1.4 kly (3.88 ± 0.42 kpc)[2]
Apparent magnitude (V)7.6[3]
Apparent dimensions (V)12′[4]
Physical characteristics
Radius18.5 ly[4]
Estimated age2.09±0.14 Gyr[2]
Other designationsCaldwell 54, Cr 170, Mel 80[5]
Map showing the location of NGC 2506

At least 94 probable members have been identified within the field of NGC 2506 based upon their radial velocities. Compared to the Sun, the cluster is moderately metal-poor with an iron abundance of [Fe/H] = –0.3 dex.[9] It shows indications of mass segregation, with the lower mass members being more likely to be in the outer parts of the cluster. This is the result of exchange of kinetic energy during encounters between the members.[10] Twelve blue straggler stars have been located in the cluster, with three of them showing short-period oscillation. Fourteen Gamma Doradus variables have been found, as well as two detached eclipsing binaries,[6] and three Delta Scuti stars.[11]

References
  1. Xin, Y.; Deng, L. (February 2005). "Blue Stragglers in Galactic Open Clusters and Integrated Spectral Energy Distributions". The Astrophysical Journal. 619 (2): 824–838. arXiv:astro-ph/0410325. Bibcode:2005ApJ...619..824X. doi:10.1086/426681.
  2. Rangwal, Geeta; et al. (November 2019). "Astrometric and photometric study of NGC 6067, NGC 2506, and IC 4651 open clusters based on wide-field ground and Gaia DR2 data". Monthly Notices of the Royal Astronomical Society. 490 (1): 1383–1396. arXiv:1909.08810. Bibcode:2019MNRAS.490.1383R. doi:10.1093/mnras/stz2642.
  3. "SEDS NGC Catalog Online". Results for NGC 2506. Retrieved 2010-11-28.
  4. O'Meara, Stephen James (2016). Deep-Sky Companions: The Caldwell Objects (2nd ed.). Cambridge University Press. p. 251. ISBN 9781316033531.
  5. "NGC 2506". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-11-28.
  6. Arentoft, T.; et al. (April 2007). "Oscillating blue stragglers, γ Doradus stars and eclipsing binaries in the open cluster NGC 2506". Astronomy and Astrophysics. 465 (3): 965–979. arXiv:astro-ph/0703111. Bibcode:2007A&A...465..965A. doi:10.1051/0004-6361:20066931.
  7. Erdmann, Robert E. "NGC Discoverers". The NGC/IC Project. Archived from the original on 2011-02-28. Retrieved 2010-11-28.
  8. Kharchenko, N. V.; et al. (2005). "Astrophysical parameters of Galactic open clusters". Astronomy and Astrophysics. 438 (3): 1163–1173. arXiv:astro-ph/0501674. Bibcode:2005A&A...438.1163K. doi:10.1051/0004-6361:20042523.
  9. Anthony-Twarog, Barbara J.; et al. (March 2018). "WIYN Open Cluster Study. LXXVI. Li Evolution Among Stars of Low/Intermediate Mass: The Metal-deficient Open Cluster NGC 2506". The Astronomical Journal. 155 (3): 21. arXiv:1802.03447. Bibcode:2018AJ....155..138A. doi:10.3847/1538-3881/aaad66. 138.
  10. Lee, S. H.; et al. (June 2013). "Deep and wide photometry of two open clusters NGC 1245 and NGC 2506: dynamical evolution and halo". Monthly Notices of the Royal Astronomical Society. 432 (2): 1672–1679. arXiv:1304.1967. Bibcode:2013MNRAS.432.1672L. doi:10.1093/mnras/stt588.
  11. Kim, S. -L.; et al. (March 2001). "Search for Variable Stars in Two Old Open Clusters: NGC2506 and NGC2420". Acta Astronomica. 51: 49–63. Bibcode:2001AcA....51...49K.

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