NGC 6649

NGC 6649
NGC 6649 by PanSTARRS
Observation data (J2000 epoch)
Right ascension18h 33m 26s[1]
Declination−10° 23′ 56″[1]
Distance4,470 ly[2] (1,370 pc[2])
Apparent magnitude (V)8.9 [1]
Apparent dimensions (V)5.0'
Physical characteristics
Estimated age60 million years[3]
Other designationsCollinder 384
Associations
ConstellationScutum
See also: Open cluster, List of open clusters

NGC 6649 is an open cluster in the constellation Scutum. It was discovered by William Herschel on 10 July, 1787. The cluster is about 40–60 million years old and it is located 4,500 light years away. Cepheid variable V367 Scuti is a member of the cluster.[4][5]

NGC 6649 is a rich cluster with more than a thousand members with apparent magnitude over 20 extending at a radial distance of about 21 arcminutes, with the core of the cluster having a radius of 2.4 arcminutes, which corresponds to 1.4 parsecs at the distance of the cluster. The tidal radius of the cluster is estimated to be 35.85±6.64 arcminutes, which corresponds to about 21 parsecs at the distance of the cluster, indicating a cluster with a dense core and an extended halo. Two smaller clusters have been detected in the vicinity of the cluster, forming a triple system.[3]

The turnoff point of NGC 6649 is estimated to be at 4.8 M☉, which corresponds to a spectral type of B5.[6] A total of 59 stars are estimated to be of spectral type B, indicating an original star mass of about 2,600 M☉.[6] Two red supergiants are also members of the cluster based on the reddening, along with a Cepheid variable, V367 Scuti.[6] Seven members of the cluster are found to be Be stars,[7] and the cluster hosts two blue straggler star candidates.[6] The metallicity of the cluster is estimated to be [Fe/H] = +0.02 ± 0.07, slightly below the expected value based on the mean galactic gradient.[6]

  1. ^ a b c "NGC 6649". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-06-19.
  2. ^ a b "WEBDA: Open cluster page". webda.physics.muni.cz. Retrieved 16 June 2024.
  3. ^ a b Gao, Xinhua (9 November 2023). "A clustering (DBSCAN+GMM) investigation of the young open cluster NGC 6649". Monthly Notices of the Royal Astronomical Society. 527 (2): 1784–1793. doi:10.1093/mnras/stad3358.
  4. ^ Turner, D. G. (February 1981). "Comments on the Cluster Main Sequence Fitting Method - Part Two - a Reexamination of the Data for NGC6649 and the Cepheid V367-SCUTI". The Astronomical Journal. 86: 231. doi:10.1086/112878.
  5. ^ Walker, A. R.; David Laney, C. (1 January 1987). "CCD photometry of galactic clusters containing Cepheid variables - IV. NGC 6649". Monthly Notices of the Royal Astronomical Society. 224 (1): 61–74. doi:10.1093/mnras/224.1.61.
  6. ^ a b c d e Alonso-Santiago, J.; Negueruela, I.; Marco, A.; Tabernero, H. M.; Castro, N. (December 2020). "Three open clusters containing Cepheids: NGC 6649, NGC 6664, and Berkeley 55". Astronomy & Astrophysics. 644: A136. arXiv:2009.12418. doi:10.1051/0004-6361/202038495.
  7. ^ Mathew, Blesson; Subramaniam, Annapurni; Bhatt, Bhuwan Chandra (21 August 2008). "Be phenomenon in open clusters: results from a survey of emission-line stars in young open clusters". Monthly Notices of the Royal Astronomical Society. 388 (4): 1879–1888. arXiv:0804.1498. doi:10.1111/j.1365-2966.2008.13533.x.