NGC 6779 / C1914+300 / Messier 56 (Updated July 2022) RA: 19:16:35.57 DEC: +30:11:00.5 (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 19:16:39.34 +30:12:16.5 R0 1.5100 15.46 1.0 V CW 2 19:16:37.35 +30:11:35.2 R0 ---- 13.92 -- V CST? Note 3 19:16:37.83 +30:12:33.9 R0 ---- 12.97 0.2 V SR Note 4 19:16:27.46 +30:08:21.1 R0 0.4236 16.06 0.28 V RR1 Note 5 19:16:36.60 +30:08:47.3 R0 ---- 12.96 0.35 V SR Note 6 19:16:35.78 +30:11:38.8 R0 88.74 12.70 1.08 V RVB Note 7 19:16:58.74 +30:07:30.9 R0 ---- 14.52 0.15 V Lb f;Note 8 19:16:28.70 +30:05:24.2 R0 ---- 14.72 0.65 V Lb f 9 19:16:50.11 +30:19:58.9 R0 ---- 13.92 0.3 V Lb f;Note 10 19:16:02.71 +30:12:25.8 R0 0.5989 17.5 1.5 B RR0 f 11 19:16:03.66 +30:15:40.4 R0 0.0756 15.88 0.5 V SXPHE f 12 19:16:17.24 +30:09:23.6 R0 0.9061 16.10 0.4 V RR0 13 19:16:38.74 +30:10:59.0 R0 38.96 14.58 -- V SR Note 14 19:16:29.84 +30:12:27.4 R0 0.3781 16.09 0.28 V RR1 15 19:16:41.55 +30:12:08.7 R0 0.0455 19.11 0.25 V SXPhe 16 19:16:34.09 +30:09:09.5 R0 0.3361 18.50 0.25 V EC f 17 19:16:34.11 +30:10:25.4 R0 0.3198 18.47 0.43 V EC 18 19:16:38.70 +30:11:09.9 R0 0.3671 15.35 -- V EC 19 19:16:30.19 +30:12:34.5 R0 0.2736 20.13 0.47 V RR1 f ======================================================================== Supplementary Notes M56 is a metal poor cluster with [Fe/H] = -1.98 (Harris 2010). Its CM diagram is characterized by a predominantly blue horizontal branch (Pietrukowicz et al. 2008 - hereafter Piet08; Deras et al 2022- herefafter Der22). With a galactic latitude, b ~ 8 degrees, the cluster is located in a rich field near the galactic plane and as a result, a significant number of the variables identified in the early investigations turned out to be field stars. The data in the above table are from the following sources. V1-12: The periods, magnitudes and amplitudes are from Wehlau & Sawyer Hogg (1985 - hereafter WSH85) unless indicated otherwise in the notes on individual stars. The RA and dec are from Samus et al. (2009). V13-19: The data are from Der22, unless indicated otherwise in the notes on individual stars. In their study, Der22 also established the membership status of the variables using Gaia-eDR3 astrometric data. Their results are indicated in the remarks column. Stars designated "f" are field stars and the others are considered to be cluster members. ========================================= Notes on individual stars V2: In his discovery paper, Shapley (1920) listed this star as a suspected variable, but no one has confirmed its variability since then. Rosino (1944) was unable to estimate its magnitudes because it was in a crowded region near the cluster centre and not resolved on his plates. WSH85 noted that its range in their data was smaller than the other SR/irregular variables. Russeva (1999) and Piet08 did not detect any variability. On the other hand, Horne (2005) found some variability but could not derive a period. Der22 showed that V2 is near the RG tip in the CM diagram and classified it as "CST?". V3: was classified as an SR variable by Rosino (1949) and by WSH85. Later, Russeva (1999) derived a period of 42.12 (or 34.86) days but different periods were derived by Horne (2005), by Piet08 and by Samus et al. (2017), who listed V3 as V0901 Lyr in the GCVS. The spacing of the observations of Der22 made them unsuitable for deriving periods longer than a few days. No period has been listed for V3 and the V magnitude and amplitude are from WSH85. V4: The period, mean V magnitude and amplitude are from Der22. V5: was classified as an SR variable by Rosino (1949) and by WSH85. Later, Russeva (1999) derived a period of 31.33 days, but different periods were derived by Horne (2005), by Piet08 and by Samus et al. (2017), who listed V3 as V0900 Lyr in the GCVS. The spacing of the observations of Der22 made them suitable for deriving periods longer than a few days. No period has been listed for V5 and the V magnitude and amplitude are from WSH85. V6: The period, mean V magnitude and amplitude are from Horne (2016). His observations were made from 2012 to 2016. Horne (2016) and Piet08 showed that the period of V6 has decreased since 1935-1955, the epoch when the early WSH85 observations were made. WSH85 derived a period of 90.0 days. A radial velocity study by Joy (1949) established that V6 is a cluster member and this was confirmed from proper motion data by Der22. V7, V9: Der22 did not publish membership status for these two stars. However, WSH85 reported that V7 and V9, as well as V8 and V11 were field stars based on a proper motion study by Rishel et al. (1981). V13: Piet08 classified V13 as a possible pulsating variable, but they had no color information for the star. Der22 showed that V13 was a cluster member located on the RG branch in the CM diagran, about a half magnitude below the RG tip. They classified it as SR. The period in the above table is from Piet08. The remaining data are from Der 22. ========================================================================= Discovery of the variable stars in M56: V1-3 Shapley (1920) with x,y coordinates and ID chart. V2 was a suspected variable. V3 was independently discovered by Davis (1917) who listed Delta RA & dec, but the x,y coordinates assigned by Shapley were different. V4-9 Sawyer (1940) with x,y coordinates and an ID chart for V1-9 as well as the numbers assigned in Kustner's (1920) catalogue. Later Sawyer (1949) classified V6 as an RV Tauri type. According to Samus et al (2009), V7, V8 and V9 are V0487, V0485 and V0486 Lyr in the Moscow GCVS. V10-11 Rosino (1944) with x, y coordinates and finding chart for V1-11 (V2 not included). According to Samus et al (2009), V10 and V11 are V0483 and V0484 Lyr in the Moscow GCVS. V12 = Kustner #68 Sawyer (1953) with x,y coordinates V13-14 Piet08 with RA and dec (J2000) V15-19: Der22 with RA and dec (J2000) and an ID chart Their ID chart also included all of the other known variables with the exception of V7, V8, V9, V10 and V11 which were outside of their field of view. ------------------ Additional variables In a series of papers, Kurochkin (1968, 1970, 1971, 1972) identified a total of 82 new variables in a field within 10 by 10 degrees of the cluster centre. WSH85 concluded that none were cluster members. Russeva (1999) announced the variability of four red giants: Kustner numbers 204, 235, 251 and K343 and derived periods in the range of 22 to 33 days for all of them. They noted that the radial velocity derived by Harris et al. (1983) for K204 indicated cluster membership. Piet08 stated that their analysis did not indicate any variability for K204, but they did not mention the other three. ======================================================================== References Davis, H. 1917, PASP, 29, 210 Deras, D., Arellano Ferro, A., Bustos Fierro, I., Yepez, M. A. 2022, Rev. Mex. A&A, 58, 121 (Der22) Harris, H., Nemec, J. M., Hesser, J. E. 1983, PASP, 95, 256 Harris, W. E. 2010, arXiv:1012.3224 Horne, J. D. 2005, JAAVSO, 34, 61 Horne, J. D. 2016, Soc. Ast. Sci. 35th Annual Symposium on Telescope Sciences, 35, 105 Joy, A. H. 1949, ApJ, 110, 105 Kurochkin, N. E. 1968, Per. Zvez. 16, 460; Kurochkin, N. E. 1970, Per. Zvez. 17, 186; Kurochkin, N. E. 1971, Per. Zvez. 17, 620 Kurochkin, N. E. 1972, Per. Zvez. 18, 497 Kustner 1920, Bonn Veroff. no. 14 Pietrukowicz, P., Olech, A., Kedzierski, P., Zloczewski, K., Wisniewski, M., Mularczyk, K. 2008, Acta A., 58, 121 (Piet08) Rishel, B. E., Sanders, W. L., Schroder, R. 1981, A&AS, 45, 443, Rosino, L. 1944, Bologna Publ. IV, No. 7 = Mem. SAI, 16, 237 Rosino, L. 1949, Bologna Publ. V, No. 12 = 1950, Mem. SAI, 21, 55 Russeva, T. 1999, IBVS, 4727 Samus, N. N., Kazarovets, E. V., Pastukhova, E. N., Tsvetkova, T. M., Durlevich, O. V. 2009, PASP, 121, 1378 Samus, N. N., Kazarovets, E. V., Durlevich, O. V. Kireeva, N. N., Pastukhova, E. N. 2017, Moscow GCVS 5.1, Astronomy Reports, vol, 61, No. 1 Sawyer, H. B. 1940, DDO Publ. 1, No. 5, 179 Sawyer, H. B. 1949, JRASC 43, 38 Sawyer, H. B. 1953, JRASC, 47, 229 Shapley, H. 1920, ApJ 52, 73 Wehlau, A. & Sawyer Hogg, H. 1985, AJ, 90, 2514 (WSH85) ========================================================================