NGC 7089: Difference between revisions

Revision as of 12:28, 29 November 2007

We^[3]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)^[4]. 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)^[5]. Finally, the HB star distribution shows that there are no significant blue HB gaps in M2.

↑ 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)
↑ 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)>
↑ Lee & Carney, Photometry of RR Lyrae Variables in M2, AJ, 117, 2868
↑ Bono, G., Caputo, F., & Marconi, M. 1995b, AJ, 110, 2365
↑ Lee, Y.-W. 1991, ApJ, 367, 524

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-'''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>, which is also called [[M2]] is a [[Globular cluster]] located in constellation [[Aquarius]].
+'''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>, which is also called [[M2]], is a [[globular cluster]] located in the constellation [[Aquarius]].
 {{Infobox NGCobject
 | number= NGC 7089