NGC 6638 / C1827-255 (Updated January 2015) RA: 18:30:56.10 DEC: -25:29:50.9 (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 18:30:01.77 -25:16:29.1 R0 ---- 15.42 0.63 P ? 2 18:30:02.58 -25:37:25.0 R0 ---- 13.22 0.39 P CST? 3 18:30:20.19 -25:37:51.4 R0 260.0 15.33 3.65 P M 4 18:30:21.75 -25:25:39.1 R0 ---- 15.76 0.68 P ? 5 18:30:31.33 -24:14:08.6 R0 ---- 15.18 0.49 P CST? 6 18:30:32.12 -25:25:46.8 R0 ---- 15.86 0.40 P CST? 7 18:30:35.42 -25:28:10.7 R0 ---- 16.59 0.57 P CST? 8 18:30:37.42 -25:36:29.6 R0 ---- 16.48 1.19 P ? 9 18:30:44.80 -25:29:05.1 R0 ---- 15.95 0.50 P CST? 10 18:30:54.36 -25:30:54.0 R0 ---- 15.92 0.44 P CST? 11 18:30:54.86 -25:32:20.4 R0 ---- 16.51 1.15 P ? 12 18:31:10.61 -25:36:27.2 R0 279.0 14.65 3.01 P M 13 18:31:14.07 -25:16:16.6 R0 209.0 14.58 4.36 P M 14 18:31:20.82 -25:14:58.3 R0 ---- 15.60 0.40 P CST? 15 18:31:37.23 -25:18:09.9 R0 156.0 15.18 3.65 P M 16 18:31:45.63 -25:20:40.3 R0 ---- 15.21 0.75 P ? 17 18:31:50.15 -25:18:00.8 R0 ---- 16.39 1.22 P ? 18 18:31:50.73 -25:26:07.2 R0 ---- 14.33 0.50 P CST? 19 18:31:53.77 -25:12:29.3 R0 ---- 15.26 0.88 P ? 20 18:30:53.00 -25:30:12.1 R0 0.3145 15.97 0.57 P RR1 21 18:30:53.68 -25:29:45.0 R0 0.3290 16.17 0.40 P RR1 22 18:30:53.91 -25:29:42.9 R0 0.3500 15.80 0.56 P RR1 23 18:30:54.18 -25:29:29.1 R0 0.3255 15.94 0.56 P RR1 24 18:30:54.58 -25:29:27.9 R0 0.6655 16.06 0.71 P RR0 25 18:30:55.56 -25:30:04.1 R0 0.6728 15.79 0.66 I RR0 Sk 26 18:30:55.64 -25:30:08.8 R0 0.6674 15.85 0.47 I RR0 Sk 27 18:30:55.91 -25:30:09.3 R0 0.5997 15.87 0.68 I RR0 Sk 28 18:30:56.03 -25:29:12.2 R0 0.3150 15.90 0.51 P RR1 29 18:30:56.11 -25:29:53.9 R0 0.2579 15.92 0.31 I RR1 Sk 30 18:30:56.47 -25:30:07.6 R0 0.5065 16.00 0.75 I RR0 Sk 31 18:30:56.64 -25:29:59.5 R0 0.4580 15.88 0.67 I RR0 Sk 32 18:30:56.57 -25:29:49.8 R0 0.5683 15.65 0.35 I RR0 Sk 33 18:30:56.91 -25:30:10.8 R0 0.3238 16.07 0.22 I RR1 Sk 34 18:30:57.37 -25:29:51.1 R0 ---- -- -- ? 35 18:30:57.77 -25:30:05.8 R0 ---- -- -- ? 36 18:30:57.98 -25:30:08.3 R0 ---- -- -- ? 37 18:30:50.43 -25:29:21.3 R0 0.2790 16.29 0.54 P RR1 38 18:30:52.13 -25:28:31.3 R0 0.3080 16.14 0.36 P RR1 39 18:30:54.24 -25:29:00.8 R0 0.2575 15.91 0.57 P RR1 40 18:30:55.09 -25:32:16.5 R0 0.2990 16.71 0.54 P RR1 mem? 41 18:30:59.14 -25:30:26.2 R0 0.2975 16.22 0.70 P RR1 42 18:30:59.49 -25:27:57.7 R0 0.3450 16.30 0.48 P RR1 43 18:31:00.41 -25:30:58.9 R0 0.2980 16.35 0.53 P RR1 mem? 44 18:31:01.1 -25:30:28 R0 0.2655 16.32 0.68 P RR1 45 18:31:02.07 -25:30:39.0 R0 0.2955 16.32 0.50 P RR1 46 18:29:58.65 -25:26:08.8 R0 ---- 16.29 1.07 P 47 18:30:00.51 -25:21:08.2 R0 ---- 16.23 0.74 P 48 18:30:00.33 -25:22:34.3 R0 ---- 13.45 1.14 P 49 18:30:06.35 -25:42:32.2 R0 ---- 14.05 1.02 P 50 18:30:21.60 -25:19:26.7 R0 ---- 15.97 0.80 P 51 18:30:21.67 -25:35:07.9 R0 ---- 16.23 1.01 P 52 18:30:30.55 -25:35:34.8 R0 ---- 16.03 1.25 P 53 18:30:44.00 -25:30:32.7 R0 ---- 15.70 0.61 P 54 18:31:05.61 -25:11:37.2 R0 ---- 14.79 1.75 P 55 18:31:04.41 -25:17:07.6 R0 ---- 15.65 0.57 P 56 18:31:17.70 -25:21:43.7 R0 ---- 14.82 1.00 P 57 18:31:16.78 -25:42:29.9 R0 380.0 16.44 1.73 P M? 58 18:31:31.36 -25:18:10.8 R0 ---- 16.17 0.96 P 59 18:31:33.25 -25:13:17.7 R0 ---- 15.19 1.67 P 60 18:31:41.31 -25:20:08.3 R0 ---- 16.35 1.31 P 61 18:31:51.37 -25:12:48.6 R0 ---- 15.58 1.70 P 62 18:31:47.43 -25:35:34.4 R0 ---- 16.03 1.25 P 63 18:31:49.49 -25:39:36.5 R0 213.0 15.36 3.28 P M 64 18:30:56.32 -25:30:03.7 R0 0.2483 16.14 0.20 I RR1 65 18:30:55.59 -25:29:43.6 R0 0.3682 15.85 0.28 I RR1 66 18:30:55.02 -25:29:47.1 R0 0.6402 15.78 0.24 I RR0 67 18:30:56.84 -25:29:46.8 R0 0.6414 15.67 0.13 I RR0 68 18:30:56.24 -25:30:04.4 R0 0.8329 15.97 0.87 I RR0 69 18:30:54.83 -25:30:01.5 R0 38.8 12.30 0.22 I SR 70 18:30:55.82 -25:30:01.0 R0 80.2 11.77 0.45 I SR 71 18:30:56.01 -25:29:57.3 R0 11.92 0.10 I L ===================================================================== Supplementary Notes A BV CM diagram by Piotto et al. (2002) based on HST data shows a blue straggler sequence and a horizontal branch that is populated on both sides of the instability strip. The RA and dec for V1-63 in the above table are from Samus et al. (2009) unless indicated "Sk" in the remarks column in which case they are from Skottfelt et al. (2015). Samus et al. pointed out that there were serious errors in the RA and dec values published earlier by Rutily & Terzan (1977). The periods, magnitudes and classifications for V1-63 are based mainly on the data of Rutily & Terzan (1977). They treated the variable stars in two groups: red variables (V1-V19 and V46-V63) and blue variables (V20-V45). Most of the red variables are located outside the tidal radius (~4.7 arcminutes according to the 2010 update of the 1996 Harris catalogue) and probably belong to the field around the cluster. Consequently they are all listed in the Moscow GCVS or NSV catalogues. Samus et al. (2009) listed the GCVS and/or NSV designations for these variables in Table 1 of their paper. Skottfelt et al. (2015) published RA, dec, periods, magnitudes and amplitudes for some of the blue variables. These stars are indicated "Sk" in the remarks column. Smith & Stryker (1986) derived radial velocities and Delta S values for a few of the RR Lyrae variables. They found that V37, V38, V42, V45 were probable members and that the membership membership status of V40 and V43 was questionable. ====================================================================== Discovery of the variable stars in NGC 6638: V1-19 Terzan (1968) with an ID chart Three of these variables #9, #10 and #11 were listed as V1-3 by Sawyer Hogg (1973) in her 3rd catalogue. The remaining 16 were not included because she considered them to be field stars. No elements were listed by Sawyer Hogg (1973) for any of the variables. Terzan's original numbering system (V1-19) has been used in the above table because it was adopted in a later paper by Rutily & Terzan (1977) for the variable stars in and around NGC 6638. The 1977 paper includes ID charts for all of the variables. V20-45 = V4-29 of Sawyer Hogg et al. (1974) and Terzan & Rutily (1975) The x,y coordinates were listed in both of the above papers. The numbers V20-45 were assigned in a later paper by Rutily & Terzan (1977). In their 1977 paper, Rutily & Terzan published an ID chart for V20-45. V46-63 Rutily & Terzan (1977) with 1950 RA and Dec and an ID chart for V1-19 and V44-63. V64-71 Skottfelt et al. (2015) with RA, dec and a finding chart ======================================================================= References Harris, W. E. 1996, AJ, 112, 1487 Piotto, G., King, I. R., Djorgovski, S. G., Sosin, C., Zoccali, M., Saviane, I., De Angeli, F. and 5 coauthors, 2002, A&A, 391, 945 Rutily, B. & Terzan, A. 1977, A&AS, 30, 315 Samus, N. N., Kazarovets, E. V., Pastukhova, E. N., Tsvetkova, T. M., Durlevich, O. V. 2009, PASP, 121, 1378 Sawyer Hogg, H. 1973, Publ. DDO, 3, No. 6 Sawyer Hogg, H., Terzan, A., Rutily, B. 1974, Comptes Rendus, 279, 333 Smith, H. A. & Stryker, L. L. 1986, PASP, 98, 453 Skottfelt, J., Bramich, D. M., Figuera Jaimes, R., Jorgensen, U. G., Kains, N., Arellano Ferro, A., Alsubai, K. A. and 27 coauthors, 2015, A&A, 573, A103 Terzan, A. 1968, Pub. Obs. Haute Prov., 9, No. 24 Terzan, A. & Rutily, B. 1975, A&A, 38, 307 =====================================================================