NGC 6539 / C1802-075 (Updated March 2015) RA: 18:04:49.74 DEC: -07:35:09.1 (J2000) ============================================================ Bytes Format Explanation 1-8 A8 Star ID 10-32 A11,1x,A11 Position 34-35 A2 Units for position R0 denotes RA, DEC in the J2000 coordinates R5 denotes RA, DEC in the 1950 coordinates XA denotes X, Y in arcseconds XP denotes X, Y in pixels 37-44 F8.4 Period (days) 46-51 F6.3 Mean magnitude (or maximum magnitude if "max" is indicated in the remarks column) 53-57 F5.3 Light amplitude (range of variability) 59 A1 Colour for mean magnitude and amplitude e.g. B, V, R, I, J, K or P (for photographic). 61-65 A5 Type of variable (draft 2006 GCVS classifications) CST denotes non variable stars previously designated as variables 67-80 A19 Notes and Remarks (f denotes field star) "--" or "----" indicates no data available ========================================================================= ID Position Period ampl C Type Notes/ RA/X Dec/Y Units Remarks ========================================================================= 1 18:04:38.16 -07:31:27.6 R0 ---- -- -- L? f?;62 2 18:04:52.03 -07:34:32.5 R0 ---- -- -- L? 58 3 18:04:43.21 -07:35:22.2 R0 ---- -- -- L? 61 4 18:04:05.14 -07:35:03.9 R0 ---- -- -- L? f?;81 5 18:04:58.64 -07:34:39.3 R0 ---- -- -- L? 34 6 18:04:48.66 -07:34:52.0 R0 ---- -- -- L? 68 7 18:04:54.87 -07:34:12.6 R0 ---- -- -- L? 53 8 18:04:51.06 -07:35:24.5 R0 ---- -- -- L? 38 9 18:04:55.79 -07:32:16.4 R0 ---- -- -- L? f?;85 10 18:04:55.09 -07:36:31.8 R0 ---- -- -- L? 49 11 18:04:50.36 -07:34:55.4 R0 ---- -- -- L? 36 PSR PSR ======================================================================== Supplementary Notes NGC 6539 is a metal rich globular cluster located in a rich, heavily reddened field near the Galactic centre. According to the 2010 update to the Harris (1996) catalogue, its [Fe/H]=-0.63 and a CM diagram by Baker et al. (2007) shows a strong red HB clump, characteristic of a metal rich cluster. The data for V1-11 are from the discovery paper by Baker et al. (2007) and the numbers in the remarks column are the ones that they used in their paper. All of these stars are considered to be long period variables. However, firm classifications could not be made because the observations were limited to a span of three nights in May and eight in June 1996 with a gap of 31 days between. Based on the cluster's high metallicity, it is possible that some of them are Mira stars. ======================================================================== Discovery of the variable stars in NGC 6539 V1-11 = variables announced by Baker et al. (2007) with RA & dec from 2MASS identifications The numbers V1-11 have been assigned in this catalogue. Baker's numbers are listed in the remarks column. Baker et al. also announced two additional variables: #14, a long period variable, and #607, an RR Lyrae. They concluded that neither is a cluster member so they are not listed in the above table. Furthermore, Layden (private communication, 2015) noted that he was uncertain about the variability of #14. It was so bright that there may have been saturation or liniarity issues with the CCD. PSR: According to Paulo Freire's website, there is a millisecond pulsar in NGC 6539. (www.naic.edu/~pfreire/GCpsr.html) ------------------------------------------------------------------ In her early catalogues, Sawyer (1939, 1955) noted that Baade had discovered one variable on Mount Wilson plates, but no further information was provided about the star. ========================================================================= References Baker, J. M., Layden, A. C., Welch, D. L., Webb, T. M. A. 2007, AJ, 133, 139 Harris, W. E. 1996, AJ, 112, 1487 Sawyer, H. B. 1939, Publ. DDO, 1, No. 4 Sawyer, H. B. 1955, Publ. DDO, 2, No. 2 =========================================================================