NGC 6838 / C1951+186 / Messier 71 (updated March 2012) RA: 19:53:46.49 DEC: +18:46:45.1 (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 19:53:56.10 +18:47:16.8 R0 190.3 14.7 2.2 B SR Note;ZSge 2 19:53:49.41 +18:44:27.0 R0 200.0 14.04 0.4 B SR Welty 3 19:53:49.34 +18:45:43.4 R0 3.7908 15.2 1.333 V EA;SX max;Note 4 19:54:04.90 +18:47:24.6 R0 ---- 14.29 -- V RR? f;Note 5 19:53:54.00 +18:47:03.4 R0 161.0 14.56 0.5 B SR Welty 6 19:53:37.69 +18:42:51.8 R0 215.0 14.12 0.4 B SR Welty;mem? 7 19:53:57.51 +18:43:34.2 R0 0.3489 18.20 -- V EW max;mem 8 19:53:57.10 +18:45:47.7 R0 0.3672 17.80 -- V EW max;mem 9 19:53:51.12 +18:47:55.8 R0 0.3739 19.07 -- V EW max;mem 10 19:53:48.98 +18:47:50.1 R0 0.5562 17.90 -- V EA max 11 19:53:34.27 +18:44:05.4 R0 0.4044 17.90 -- V EW max;mem 12 19:53:48.16 +18:47:50.4 R0 0.0500 16.18 0.12 V SXPHE max 13 19:53:48.57 +18:47:40.3 R0 0.0582 19.38 -- V SX? max 14 19:53:44.97 +18:39:32.3 R0 0.3217 18.61 -- V EW max 15 19:53:48.64 +18:45:45.8 R0 ---- 17.78 -- V SXPHE max 16 19:54:01.75 +18:47:18.6 R0 0.7684 15.24 -- V EW max 17 19:54:06.22 +18:49:01.5 R0 0.2445 20.35 0.7 V EW max 18 19:53:14.13 +18:39:29.1 R0 0.2400 18.08 0.7 V EW max 19 19:53:17.15 +18:52:48.2 R0 0.2236 17.35 0.15 V SXPHE max 20 19:53:21.11 +18:42:42.3 R0 ---- 18.45 0.3 V EB? max 21 19:53:53.16 +18:52:23.9 R0 ---- 18.40 0.20 V EB? max 22 19:53:58.97 +18:49:29.0 R0 0.3970 16.6 -- V SX? max 23 19:54:00.28 +18:52:35.3 R0 0.2745 19.05 0.3 V EB max 24 19:54:09.29 +18:43:33.0 R0 0.2290 19.20 0.5 V EB max 25 19:54:09.61 +18:47:21.8 R0 ---- 18.7 -- V EB? max 26 19:53:23.42 +18:42:10.7 R0 0.3990 16.20 -- V EB max 27 19:53:25.56 +18:51:17.5 R0 0.3530 16.16 -- V EW max 28 19:53:48.67 +18:45:58.4 R0 0.0500 15.89 -- V SX? max 29 19:53:57.65 +18:42:51.1 R0 ---- 16.6 -- V EB max PSR ---- ---- ---- -- -- MSP rotP=4.89ms =================================================================== Supplementary Notes The RA and dec for V1-6 are from Samus et al. (2009) and for V7-29, they are from Park & Nemec (2000). On the numbering system of Park & Nemec, V7-29 were V1-23. The periods, mean magnitudes and amplitudes for V2, V5 and V6 are from Welty (1985) who considered V2 and V5 to be cluster members, but concluded that the membership of V6 (V0345 Sge) is unlikely based on a proper motion study by Cudworth (1985). The remaining data for V1, 3 and 4 are discussed in the notes on individual stars. The periods, magnitudes, amplitudes and classifications for V7-29 are from the study by Park & Nemec (2000). The membership status of V7, 8, 9 and 11 is from Rucinski (2000). He did not analyse any of the other variables. =================================================================== Notes on individual stars V1 = Z Sge: The period, mean magnitude and amplitude are from Mantegazza (1988). Pogossiantz (1983) derived two periods for this stars: 175.3 days before JD 2438700 and 190.8 days afterwards. However, Mantegazza concluded that a better interpretation of the data was that the light variations resulted from the superimposition of two modes with periods 190.3 and 176.4 respectively. V3 = QU Sge: On the basis of a radial velocity study, Liller & Tokarz (1981) concluded that V3 is not a cluster member. However, Jeon et al. (2006) questioned this conclusion. They also presented evidence that the binary star has an SXPhe component with P~0.03 days and a V amplitude of 0.024 mag. V4 = NSV 24932 Sawyer Hogg (1973) classified this star as a possible RR Lyrae variable. Cudworth (1985) derived its BV magnitudes and concluded that it was a field star, based on its proper motion. =================================================================== Discovery of the variable stars in NGC 6838:: V1-2 = Z Sge and 48.1928 Sge Baade (1928) with 1925 RA and dec Sawyer (1952) pointed out that these two variables were within the limits of the cluster NGC 6838 and Sawyer (1953) assigned the numbers V1 and 2 V3-4 Sawyer (1953) with x,y coordinates and an ID chart for V1-4 V5-6 = AH1-29, S142 [V6 is also known as V0345 Sge.] Welty (1985) recognized that these two stars were variable and derived periods and x,y coordinates (offset by -5,+11 from Sawyer Hogg's x,y system). Frogel et al. (1979) had previously pointed out that AH1-29 was a small amplitude variable near the RG tip and in 1977, there was some private correspondence between Cohen and Sawyer Hogg concerning this star. AH1-29 was identified on a chart by Arp & Hartwick (1971) and S142 was identified by Sanders (1971) The numbers V5 and V6 were assigned in the electronic catalogue (Clement 2001) V7-11 = V1-5 of Yan & Mateo who listed their 1950 RA and Dec and published ID charts. Yan & Mateo's V3 and V4 had been previously announced by Hodder et al. (1992) who designated them as H3 and H4 and published X,Y pixel numbers and an ID chart. Rucinski (2000) analysed the observations of the 4 contact binaries (Yan & Mateo V1,2,3,5 = V7,8,9,11) and concluded that they were all cluster members based on their photometric properties. The numbers V7-11 were assigned in our electronic catalogue (Clement et al. 2001). V12-13 = V6-7 of Park & Nemec (2000), previously announced by Hodder et al. (1992) who designated them as H1 and H2 and published X,Y pixel numbers and an ID chart. The numbers V12-13 were assigned in our electronic catalogue (Clement et al. 2001). V14-29 = V8-23 of Park & Nemec (2000) who listed RA, dec and published ID charts. The numbers V14-29 were assigned in our electronic catalogue (Clement et al. 2001). PSR = PSR J1953=1846A, a binary millisecond pulsar with a low mass companion (Hessels et al. 2007): rotation P= 4.888 ms and orbital P = 4.24 hours ------------------------------------------------------------------- Jeon et al. (2004) announced the discovery of a double-radial-mode SX Phe star which they named D6, but no identification was provided and the star was not mentioned in their subsequent paper (Jeon et al. 2006) on SX Phe variables in M71. ------------------------ Jeon et al. (2007) announced the detection of 24 eclipsing binaries, 10 of them new discoveries and 16 other variables, most of which have long periods. No further information was given. ----------------------- Huang etal. (2010) searched for HST counterparts to Chandra X-ray sources in M71 and concluded that source #29 is a CV and that source #02 and #20 are chromospherically active binaries. There were not successful in identifying the optical counterpart for the MSP. ==================================================================== References Arp, H. C. & Hartwick, F. D. A. 1971, ApJ, 167, 499 Baade, W. 1918, AN, 232, 65 Clement, C. M., Muzzin, A., Dufton, Q., Ponnampalam, T., Wang, J., Burford, J., Richardson, A., Rosebery, T. 2001, AJ, 122, 2587 Cudworth, K. M. 1985, AJ, 90, 65 Frogel, J.A., Persson, S. E., Cohen, J. G. 1979, ApJ, 227, 499 Hessels, J. W. T., Ransom, S. M., Stairs, I. H., Kaspi, V. M., Freire, P. C. C. 2007, ApJ, 670, 363 Huang, R. H. H., Becker, W., Edmonds, P. D., Elsner, R. F., Heinke, C. O., Hsieh, B. C. 2010, A&A, 513, A16 Jeon, Y.-B., Lee, M. G., Kim, S.-L., Lee, H. 2004, ASPConf, 310, 166 Jeon, Y.-B., Kim, S.-L., Lee, M. G., Lee, H., Lee, J. W. 2006, ApJ, 636, L129 Jeon, Y.-B., Kim, S.-L., Lee, C.-U. 2007, IAU Symp, 240, 428 Liller, M. H. & Tokarz, S. P. 1981, AJ, 86, 669 Mantegazza, L. 1988, A&A, 196, 109 Park, N.-K. & Nemec, J. M. 2000, AJ, 119 1803 Pogossiantz, A. Y. 1983, Per. Zvez., 1983, 22, 85 Rucinski, S. M. 2000, AJ, 120, 319 Sanders, W. L. 1971, 1971, A&A, 15, 173 Sawyer, H. B. 1952, AJ, 57, 26 Sawyer, H. B. 1953, JRASC, 47, 229 Welty, D. E. 1985, AJ, 90, 2555 =====================================================================