NGC 6626 / Messier 28 / C1821-249 (Updated 2009) RA: 18:24:32.81 DEC: -24:52:11.2 (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 variablility) 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 18:24:45.23 -24:48:57.9 R0 0.4916 15.91 1.1 V RR0 Note 2 18:24:29.16 -24:51:06.6 R0 ---- 12.67 0.7 V LB 3 18:24:30.18 -24:50:18.5 R0 ---- 12.67 0.25 V LB Note 4 18:24:30.11 -24:51:36.5 R0 13.462 14.21 1.0 B CW 5 18:24:29.50 -24:51:53.0 R0 0.6444 15.52 0.8 V RR0 6 18:24:35.16 -24:51:18.1 R0 ---- 12.63 0.7 V LB 7 18:24:44.48 -24:50:25.1 R0 320.0 15.1 3.3 V M f;Note 8 18:24:49.61 -24:55:48.3 R0 0.5660 15.71 1.3 V RR0 9 18:24:21.29 -24:56:24.2 R0 0.6615 14.60 0.4 V RR0 10 18:24:39.52 -24:53:26.3 R0 ---- 12.14 0.6 V LB Note 11 18:24:31.5 -24:51:33 R0 0.5428 15.78 1.2 V RR0 12 18:24:43.31 -24:52:56.0 R0 0.5782 15.61 1.4 V RR0 13 18:24:25.77 -24:52:33.6 R0 0.6549 15.69 1.0 V RR0 14 18:24:23.86 -24:53:54.5 R0 ---- 16.02 0.2 V NV? 15 18:23:56.81 -24:55:10.3 R0 0.4489 16.73 1.1 V RR0 f 16 18:25:04.86 -24:58:20.4 R0 0.6727 16.63 0.8 V RR0 f 17 18:24:35.83 -24:53:15.9 R0 91.7 11.9 0.75 V RV Note 18 18:24:36.55 -24:51:46.5 R0 0.6402 15.75 1.15 V RR0 19 18:24:30.8 -24:51:57 R0 0.335 16.05 0.5 B RR1 W&SH 20 18:24:33.06 -24:51:42.9 R0 0.4977 15.4 0.9 B RR0 W&SH 21 18:24:32.95 -24:51:58.8 R0 29.93 14.75 1.5 B CW W&SH 22 18:24:31.0 -24:52:03 R0 0.9954 15.4 0.75 B CW? W&SH 23 18:24:30.27 -24:52:02.9 R0 0.2923 15.9 0.5 V RR1 24 18:23:59.58 -24:49:35.6 R0 0.5104 16.45 1.2 V RR0 f PSR 18:21:27.5 -24:53:51.0 R5 ---- -- -- Note ============================================================================= Supplementary Notes and References For V1-24, the period, magnitude, amplitude, variability type and membership status are from Wehlau & Butterworth (1990, AJ 100, 686) unless indicated W&SH in the remarks column in which case they are from from Wehlau & Sawyer Hogg (1984, AJ 89, 1005) The RA and dec for V1-24 were estimated by Brian Skiff (private communication). He used the ID charts of Wehlau & Sawyer Hogg (1984) to identify the variables in astrometric catalogs: 2MASS for V1-8, V10, V12-16, V18, V21, V23-24 Denis (1999 A&A 349, 236) for V9, V20 UCAC2 (2004 AJ 127, 3043) for V17 SkyView estimate (+/-1") for V11, V19, V22 Brian Skiff has also provided GCVS names for V7 (V4137 Sgr), V15 (V4128 Sgr), V16 (V4130 Sgr), V17 (V2342 Sgr) and V24 (V4129 Sgr). ====================== Notes on individual stars V1, V3, V10, V17: In a proper motion study of M28, Rees & Cudworth (1991, AJ 102, 152) found membership probabilities for V1 (90%), V3 (57%), V10 (90%) and V17 (94%). V7: The RA and dec refer to the SE component of a close pair PSR: The coordinates listed above refer to PSR 1821-24 which was discovered by Lyne et al. (1987, 1987, Nature 328, 399). Another 10 pulsars have subsequently discovered in M28. See below. ============================================================================= Discovery of the variable stars in M28 V1-9 Bailey (1902, Harvard Ann 38) with x,y positions (page 242) and ID chart (Plate XI, Fig. 3) V10-16 Sawyer (1949, AJ 54, 193) with x,y positions V17 = Star #5 of Hoffleit (1965, AJ 70, 307) and star 63a of Hoffleit (1972, IBVS 660) The number V17 was assigned by Sawyer Hogg (1973) in her 3rd catalog and the x,y coordinates were derived by Wehlau & Sawyer Hogg (1982, IBVS 2171). V18, V20, V21, V24 Wehlau & Sawyer Hogg, IBVS 2171 (1982) with x,y positions These authors pointed out that the star listed as V18 in Sawyer Hogg's (1973) 3rd catalogue is V12. They also listed coordinates for three other variables that they designated V19, V22 and V23. However, in a subsequent study (1984, AJ 89, 1005), they found that these three stars were not variable. V19, V22, V23 Wehlau & Sawyer Hogg (1984, AJ 89, 1005) with x,y positions for these variables and ID charts for V1-24 PSR A millisecond pulsar was discovered in M28 by Lyne et al. (1987, Nature 328, 399) with 1950 RA, dec and ID chart. According to Ransom (2008, AIPConference Proceedings 983, 415) and (2007, IAU Symp 246, 291), there are now 11 pulsars known in M28. The additional 10 were announced by Stairs et al. (2006, AAS Bulletin 38, 1118) based on a 2006 PhD thesis by S. Begin. Coordinates and other information about these pulsars were published by Becker & Hui (2007, astroph arXiv:0705.0119v1) They did not include info about one of them (PSR-K) because Begin did not publish its coordinates in the thesis. Rees & Cudworth (1991, AJ 102, 152) found strong evidence for variation of 3 additional stars (their RC133, 2-56 and RC11). ===================================================================