NGC 6809 / C1936-310 / Messier 55 (Updated March 2010) RA: 19:39:59.71 DEC: -30:57:53.1 (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 or P (for photographic). 61-65 A5 Type of variable (draft 2006 GCVS classifications) NV denotes not variable 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 19:40:22.45 -30:58:24.3 R0 0.5800 14.38 1.28 V RR0 2 19:39:42.24 -30:57:57.5 R0 0.4061 14.41 0.44 V RR1 3 19:40:05.27 -31:02:34.5 R0 0.6620 14.28 0.85 V RR0 4 19:40:07.43 -30:56:32.1 R0 0.3842 14.33 0.40 V RR1 5 19:39:55.89 -30:58:44.4 R0 0.3761 14.32 0.43 V RR1 6 19:40:07.69 -30:57:50.0 R0 0.3888 14.38 0.47 V RR1 7 19:39:59.89 -30:57:33.1 R0 0.6826 14.26 1.03 V RR0 8 19:40:02.08 -30:58:58.4 R0 0.7220 14.37 0.62 V RR0 9 19:40:27.38 -30:57:59.1 R0 0.3163 14.43 0.41 V RR1 Note 10 19:40:08.51 -30:54:49.0 R0 0.3318 14.41 0.31 V RR1 Note 11 19:40:12.02 -30:56:14.1 R0 0.3100 14.42 0.21 V RR1 12 19:39:59.80 -30:58:02.7 R0 0.3259 14.34 0.26 V RR1 Note 13 19:39:53.08 -30:50:30.6 R0 0.3978 14.44 0.39 V RR1 14 19:39:54.76 -30:50:10.2 R0 0.5216 17.97 1.03 V RR0 f;Sgr 15 19:39:43.95 -31:00:36.3 R0 0.6373 18.33 0.40 V RR0 f;Sgr 16 19:40:09.20 -30:56:42.0 R0 0.0534 16.94 0.016 V SXPHE 17 19:40:11.33 -30:59:25.1 R0 0.0413 17.18 0.049 V SXPHE 18 19:40:06.87 -30:56:32.1 R0 0.0466 16.98 0.029 V SXPHE 19 19:39:57.67 -30:57:01.3 R0 0.0382 17.27 0.033 V SXPHE 20 19:39:54.95 -30:58:21.3 R0 0.0332 17.04 0.102 V SXPHE 21 19:39:58.27 -30:59:06.1 R0 0.1356 15.76 0.036 V SXPHE 22 19:40:07.80 -31:00:12.6 R0 0.0456 16.81 0.337 V SXPHE 23 19:39:51.82 -30:55:52.8 R0 0.0414 17.22 0.050 V SXPHE 24 19:39:45.49 -30:56:02.7 R0 0.0418 17.06 0.026 V SXPHE 25 19:39:51.55 -30:56:21.3 R0 0.0985 15.88 0.899 V SXPHE 26 19:39:47.06 -30:57:34.0 R0 0.0820 16.11 0.173 V SXPHE 27 19:39:54.05 -30:58:07.5 R0 0.0410 17.09 0.029 V SXPHE 28 19:40:15.04 -31:05:15.0 R0 0.0538 20.61 0.260 V SXPHE f;Sgr 29 19:39:42.58 -30:55:58.3 R0 0.0343 20.71 0.295 V SXPHE f;Sgr 30 19:39:41.02 -30:50:25.2 R0 0.0563 20.35 0.258 V SXPHE f;Sgr 31 19:40:00.99 -30:57:56.5 R0 0.0388 17.23 0.041 V SXPHE 32 19:39:58.14 -30:58:32.7 R0 0.0415 16.92 0.097 V SXPHE 33 19:39:54.56 -30:59:57.9 R0 0.0593 16.40 0.054 V SXPHE 34 19:40:01.02 -31:00:37.9 R0 0.0370 17.23 0.029 V SXPHE 35 19:39:50.37 -30:55:12.4 R0 0.0487 16.57 0.070 V SXPHE 36 19:39:48.56 -30:56:45.0 R0 0.0394 16.74 0.067 V SXPHE 37 19:39:49.87 -30:57:42.5 R0 0.0438 16.96 0.051 V SXPHE 38 19:39:58.86 -30:58:14.8 R0 0.0392 16.69 0.044 V SXPHE Note 39 19:40:11.99 -31:02:04.5 R0 0.0358 17.21 0.034 V SXPHE 40 19:40:01.90 -30:55:38.2 R0 0.0370 17.20 0.028 V SXPHE 41 19:40:02.95 -30:58:28.3 R0 0.0452 16.53 0.106 V SXPHE Note 42 19:39:58.61 -30:57:23.9 R0 0.0367 17.16 0.053 V SXPHE 43 19:40:08.59 -30:58:51.1 R0 ---- 18.98 2.90 V UG max;Note =================================================================== Supplementary Notes and References All the data listed for V1-V15 are from Olech et al. (1999, AJ 118, 442). The data for V16-V42 are from the discovery paper by Pych et al. (2001, A&A 367, 148). They classified V16-V30 as single-mode SXPhe variables and V31-V42 as double-mode SXPhe variables. For all of the double-mode stars (except V41), one of the modes is considered to be non-radial in origin. The periods listed for V31-V42 in the above table are the longer of the stars' two periods and the amplitudes are the amplitudes associated with these longer periods (except in the case of V38). ====================================== Notes on individual stars V9, V10, V12: Olech et al. (1999, AJ 118, 442) found evidence for non-radial pulsations in these three variables. V38: The period listed is the longer period, but the amplitude corresponds to the shorter period. V41: Pych et al. (2001) tentatively concluded that this star is pulsating in the first and second radial overtone modes. V43: This is the star CV1 announced by Kaluzny et al. (2005, MNRAS 359, 677). The data in the table are from their paper. ===================================================================== Discovery of the variable stars in M55: V1-2 Bailey (1902, Harvard Annals 38, 1) with x,y coordinates (page 243) and an ID chart (plate XII: Fig 1, page 252.23, description on page 251) V3-6 King (1951, Harvard Bulletin 920, 16) with x,y coordinates. No finding chart was provided, but in a later paper (King & Bruzual, 1976, A&A 50, 459) he pointed out that Figures 2 and 3 in a paper by Alcaino (1975, A&A Suppl 22, 193) serve as convenient finding charts. V1-V6 are equivalent to Alcaino #59, 366, 96, 433, 592, and 456, respectively. V7-V15 Olech et al. (1999, AJ 118, 442) with RA, dec and findng charts. V16-42 Pych et al. (2001, A&A 367, 148) with RA, dec and finding charts V43 = CV1 (a dwarf nova) Kaluzny et al. (2005, MNRAS 359, 677) with RA, dec and finding chart. These authors also detected a blue variable (M55-B1) that they concluded might be a candidate quasar. The extragalactic nature of this source was confirmed by Webb et al. (2006, A&A 445, 155). It was their X-ray source #39. =============================================================== Additional candidate variables Webb et al. (2006, A&A 445, 155) identified 47 X-ray sources in the vicinity of M55 with XMM-Newton, four within the core radius (2.83 arcmin) and one at the half mass radius (2.89 arcmin). In their Table 7, they classified the sources that might be related to M55. They concluded that their source #30 was the Kaluzny et al. dwarf nova. In their Table 6, they listed sources that had varied since Rosat observations obtained in 1993. Bassa et al. (2008, A&A 488, 921) identified 16 X-ray sources within the half mass radius, based on Chandra data. They expected about half of these to be background sources. Their CX1 was the dwarf nova announced by Kaluzny et al. They concluded that their source CX2 could be a faint cataclysmic variable and CX7, CX10 and CX16 might be associated with active binaries.