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, 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 19:53:56.10 +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;f? P1 19:53:57.51 +18:43:34.2 R0 0.3489 18.20 -- V EW max;mem P2 19:53:57.10 +18:45:47.7 R0 0.3672 17.80 -- V EW max;mem P3 19:53:51.12 +18:47:55.8 R0 0.3739 19.07 -- V EW max;mem P4 19:53:48.98 +18:47:50.1 R0 0.5562 17.90 -- V EA max P5 19:53:34.27 +18:44:05.4 R0 0.4044 17.90 -- V EW max;mem P6 19:53:48.16 +18:47:50.4 R0 0.0500 16.18 0.12 V SXPHE max P7 19:53:48.57 +18:47:40.3 R0 0.0582 19.38 -- V SX? max P8 19:53:44.97 +18:39:32.3 R0 0.3217 18.61 -- V EW max P9 19:53:48.64 +18:45:45.8 R0 ---- 17.78 -- V SX? max P10 19:54:01.75 +18:47:18.6 R0 0.7684 15.24 -- V EW max P11 19:54:06.22 +18:49:01.5 R0 0.2445 20.35 0.7 V EW max P12 19:53:14.13 +18:39:29.1 R0 0.2400 18.08 0.7 V EW max P13 19:53:17.15 +18:52:48.2 R0 0.2236 17.35 0.15 V SXPHE max P14 19:53:21.11 +18:42:42.3 R0 ---- 18.45 0.3 V EB? max P15 19:53:53.16 +18:52:23.9 R0 ---- 18.40 0.20 V EB? max P16 19:53:58.97 +18:49:29.0 R0 0.3970 16.6 -- V SX? max P17 19:54:00.28 +18:52:35.3 R0 0.2745 19.05 0.3 V EB max P18 19:54:09.29 +18:43:33.0 R0 0.2290 19.20 0.5 V EB max P19 19:54:09.61 +18:47:21.8 R0 ---- 18.7 -- V EB? max P20 19:53:23.42 +18:42:10.7 R0 0.3990 16.20 -- V EB max P21 19:53:25.56 +18:51:17.5 R0 0.3530 16.16 -- V EW max P22 19:53:48.67 +18:45:58.4 R0 0.0500 15.89 -- V SX? max P23 19:53:57.65 +18:42:51.1 R0 ---- 16.6 -- V EB max P24 PSR ---- ---- ---- -- -- MSP rotP=4.89ms =================================================================== Supplementary Notes The RA and dec for V1-6 are from Samus et al. (2009) and for P1-23, they are from Park & Nemec (2000). In the above table, P1-23 are v1-23 on the numbering system of Park & Nemec and V7-29 in the paper by Samus et al. 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 star: 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. A K-band light curve plotted by Sloan et al. (2010) with a period of 179 days shows considerable scatter, which supports this conclusion. 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. Cudworth (1985) derived 51% probability of membership based on proper motion. 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). S142 was identified by Sanders (1971). The numbers V5 and V6 were assigned by Clement (1997) in the first electronic update of the Sawyer Hogg (1973) catalogue. P1-5 = short period variables V1-5 of Yan & Mateo (1994) = faint variables v1-5 of Park & Nemec (2000) Yan & Mateo listed their 1950 RA and Dec and published ID charts. Park & Nemec listed their 2000 RA and dec and published ID charts for V1, V2, V4 and V5. 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 ) and concluded that they were all cluster members based on their photometric properties. In the Clement et al. (2001) catalogue, the numbers V7-11 were assigned to these stars and Samus et al. (2009) followed the Clement numbering system. However, subsequent investigators have followed the numbering system of Yan & Mateo. Therefore in this electronic catalogue, these stars are numbered P1-5 to distinguish them from the original V1-5 in NGC 6838 (M71). P6-7 = faint variables 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. In the Clement et al. (2001) catalogue, the numbers V12-13 were assigned to these stars and Samus et al. (2009) followed the Clement numbering system. However, subsequent investigators have followed the numbering scheme that Park & Nemec (2000) set up for the faint variables in M71 so they have been numbered P6-7 in this catalogue. P8-23 = v8-23 of Park & Nemec (2000) who listed RA, dec and published ID charts. In the Clement et al. (2001) catalogue, the numbers V14-29 were assigned to these stars and Samus et al. (2009) followed the Clement numbering system. However, in a subsequent paper, McCormac et al. (2014) followed the numbering system of Park & Nemec. Therefore in this electronic catalogue, the stars are designated "P" to indicate the numbering system of Park & Nemec. P24-40 = V24-40 of McCormac et al. (2014) who published finding charts and 2000 RA and dec 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. This was a poster paper and only the abstract was published. ----------------------- Elsner et al. (2008) observed the cluster with Chandra and detected 29 X-ray sources within the half-mass radius (r_h) and another 34 between r_h and 2r_h. Their source s08 coincideed with the MSP. For some of the other sources, they listed possible optical and infrared counterparts. ----------------------- Pietrukowicz (2009) imaged five of the X-ray sources in H-alpha and concluded that s57 of Elsner et al. (2008) might be a CV. ----------------------- 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. 1997, AAS Newsletter, 84, 15 Clement, C. 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