NGC 6540 / Djorg3 / C1802-277 (Updated March 2016) RA: 18:06:08.6 DEC: -27:45:55 (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 18:06:08.22 -27:45:52.2 R0 0.2541 15.137 0.285 I RR1 2 18:06:09.00 -27:45:25.7 R0 0.4498 15.184 0.555 I RR0 3 18:06:09.59 -27:46:08.7 R0 0.5013 14.989 0.533 I RR0 ======================================================================= Supplementary Notes NGC 6540 was thought to be an open cluster until Bica et al. (1994) showed it to be a thick disk globular cluster. A near IR (K, J-K) CM diagram published by Valenti et al. (2010) is characterized by a steep poorly populated RGB and a blue HB which was also present in the optical CMD of Bica et al. (1994). They estimated [Fe/H]=-1.29, based on the slope of the RGB, a value that is in agreement with [Fe/H] = -1.40 +/- 0.40 derived by Cote (1999) for four stars from the equivalent of a few Fe I lines. The data for the RR Lyrae variables are from the OGLE IV survey (Soszynski et al. 2014). ===================================================================== Discovery of the Variable Stars in NGC 6540 V1-3 = OGLE-BLG-RRLYR-13297, OGLE-BLG-RRLYR-13300, OGLE-BLG-RRLYR-13306 identified by RA and dec in the OGLE III survey (Soszynski et al. 2011a). The numbers V1-3 have been assigned in this catalogue. ---------------------------------------------------------------------- The OGLE III investigation of the Galactic Bulge also included catalogues of Type II Cepheids (Soszynski et al 2011b) and Long Period variables (Soszynski et al. 2013). In these surveys, no variables were announced within 0.8 arcminutes of NGC 6540, the radius listed by Soszynski et al. (2011a). ====================================================================== References Bica, E., Ortolani, S., & Barbuy, B. 1994, A&A, 284, 67 Cote, P. 1999, AJ, 118, 406 Soszynski, I., Dziembowski, W. A., Udalski, A., Poleski, R., Szymanski, M. K., Kubiak, M., Pietrzynski, G. and 4 coauthors, 2011a, Ac. A., 61, 1 Soszynski, I., Udalski, A., Pietrukowicz, P., Szymanski, M. K., Kubiak, M., Pietrzynski, G. , Wyrzykowski, L. and 3 coauthors, 2011b, Ac. A., 61, 285 Soszynski, I., Udalksi, A., Szymanski, M. K., Kubiak, M., Pietrzynski, G., Wyrzykowski, L., Ulaczyk, K. and 3 coauthors, 2013, Acta A., 63, 21 Soszynski, I., Udalski, A., Szymanski, M. K., Pietrukowicz, P., Mroz, P., Skowron, J., Kozlowski, S. and 6 coauthors, 2014, Ac. A. 64, 177 Valenti, E., Ferraro, F. R. & Origlia, L. 2010, MNRAS, 402, 1729 ===============================================================