imported>Thorsten Alteholz |
imported>Thorsten Alteholz |
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| {{subpages}} | | {{subpages}} |
| '''NGC 7089'''<ref>Hirshfeld, Alan, and Roger W. Sinnott, eds., Sky Catalogue 2000.0, Vol.2, Cambridge, Massachusetts: Sky Publishing Corp. and Cambridge University Press, 1985. (3098,238)</ref><ref>NGC 2000.0, The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J.L.E. Dreyer Sinnott, R.W. (edited by) <Sky Publishing Corporation and Cambridge University Press (1988)></ref>, also known as '''M2''', is a [[globular cluster]] located in the constellation [[Aquarius]]. | | '''NGC 7089''', also known as '''M2''', is a [[globular cluster]] located in the constellation [[Aquarius]]. |
| {{Infobox NGCobject | | {{Infobox NGCobject |
| | number= NGC 7089 | | | number= NGC 7089 |
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| | type = [[Globular cluster]] | | | type = [[Globular cluster]] |
| | epoch = 2000.0 | | | epoch = 2000.0 |
| | ra = 21<sup>h</sup>33.5<sup>m</sup> | | | ra = |
| | de = -00<sup>o</sup>49<sup>'</sup> | | | de = |
| | app_size = 12.9 | | | app_size = |
| | app_mag = 6.5 | | | app_mag = |
| | distance_ly = | | | distance_ly = |
| | const = Aquarius | | | const = Aquarius |
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| | redshift = | | | redshift = |
| | other = M 2 | | | other = M 2 |
| | source = Hirshfeld, Alan, and Roger W. Sinnott, eds., Sky Catalogue 2000.0, Vol.2, Cambridge, Massachusetts: Sky Publishing Corp. and Cambridge University Press, 1985. (3098,238) | | | source = |
| | org_source = NGC 2000.0, The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J.L.E. Dreyer Sinnott, R.W. (edited by) <Sky Publishing Corporation and Cambridge University Press (1988)> | | | org_source = |
| }} | | }} |
| === Appearance === | | === Appearance === |
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| === Scientific research === | | === Scientific research === |
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| * We<ref>Lee & Carney, Photometry of RR Lyrae Variables in M2, AJ, 117, 2868</ref>have presented BV photometry for 30 RR Lyrae variables, including 13 newly discovered variables, in the Oosterhoff type II globular cluster M2. The methods of searching for periods and new variables were discussed. We have derived pulsational parameters for RR Lyrae variables. With the discovery of new RR Lyrae variables, the mean periods of the RRab and RRc variables are 〈Pab〉 = 0.69 ± 0.02 days and 〈Pc〉 = 0.33 ± 0.01 days, respectively. The number ratio of the RRc type variables to the total number of the RR Lyrae type variables is n(c)/n(ab + c) = 0.40. A comparison with the model instability boundaries shows general agreement, although the detailed comparison is somewhat uncertain in the theoretical fundamental red edge given by Bono et al. (1995b)<ref>Bono, G., Caputo, F., & Marconi, M. 1995b, AJ, 110, 2365</ref>. The RR Lyrae pulsational mode transition occurs between the fundamental period of 0.528 days and 0.556 days. From the star counts along the horizontal branch, two HB color distribution indices have been derived, (B-R)/(B + V + R) = 0.92 and B2/(B + V + R) = 0.46. Our analysis of the secular period-change rates from six RRab variables shows a general agreement with the canonical synthetic HB model predictions by Lee (1991)<ref>Lee, Y.-W. 1991, ApJ, 367, 524</ref>. Finally, the HB star distribution shows that there are no significant blue HB gaps in M2.
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| === References === | | === References === |
| {{reflist}} | | {{reflist}} |
