NGC 6637 / C1828-323 / Messier 69 (Updated June 2014) RA: 18:31:23.10 DEC: -32:20:53.1 (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, 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 18 31 21.73 -32 21 03.1 R0 ---- 14.00 2.0 P LB 2 18 31 04.34 -32 17 29.8 R0 0.4756 16.60 1.4 P RR0 f;V3484Sgr 3 18 31 20.34 -32 22 15.8 R0 ---- 15.20 1.2 P LB 4 18 31 21.88 -32 22 27.7 R0 200.0 7.86 0.58 K M 5 18 31 23.44 -32 20 49.4 R0 198.0 7.82 0.73 K M 6 18 31 21.75 -32 19 54.6 R0 ---- 14.05 -- V LB 7 18 31 30.04 -32 20 50.5 R0 ---- 13.13 -- V LB 8 18 31 23.45 -32 21 26.1 R0 ---- 13.36 -- V LB ================================================================ Supplementary Notes NGC 6637 is a metal rich bulge cluster with [Fe/H]= -0.8 (Minniti 1995). A VI CM diagram published by Heasley et al. (2000) shows a pronounced red HB. The RA and dec for V1-8 are from Samus et al. (2009). The remaining data are from the following sources. V1-3: The magnitudes listed for V1-V3 are from Rosino (1962). V2: The period for V2 (V3484 Sgr) is from the GCVS. Hartwick & Sandage classified the RR Lyrae V2 as a field star because it is more than 5 arcmin from the cluster centre and at least a magnitude fainter than the HB. V4-5: The periods, magnitudes and amplitudes listed for V4-V5 are from Sloan et al. (2010). The Mira classification for these variables was by Lloyd Evans & Menzies (1971). Catchpole et al. (1970) derived their radial velocities and concluded that both stars were plausible cluster members and probably Mira variables. V5: This star was numbered V10 by Rosino (1962) in his discovery paper. The number V5 was assigned by Sawyer Hogg in her 3rd (1973) catalogue because Rosino considered his V5-V9 to all be field stars. The star referred to as V10 by Catchpole et al. (1970) and by Lloyd Evans & Menzies (1971, 1973) is V5 because their work was published before Sawyer Hogg assigned the new numbering system. V6-8: The magnitudes listed for V6-8 are from Hartwick & Sandage (1968). ===================================================================== Discovery of the variable stars in NGC 6637: V1-3 Rosino (1962) with x,y coordinates and ID chart V2=V3484 Sgr and is listed in the GCVS. V4 = V1894 Sgr = Ponsen Star 69 Ponsen (1957) with 1900 RA and Dec Rosino (1962) assigned the number V4 and published x,y coordinates and an ID chart. V5 = Rosino V10 Rosino (1962) with x, y coordinates and an ID chart The number V5 was later assigned by Sawyer Hogg in her 3rd catalogue. Rosino (1962) published data for 10 variables, which he numbered V1 t0 V10, but five of them were considered to be field stars, based on their brightness and their distance from the cluster centre. According to Catchpole et al. (1970), the star that Hartwick & Sandage (1968) identified as V10 is not variable. V6-8 = II-37, III-43 (annulus 1' -2') and IV-11 (inner 1') of Hartwick & Sandage (1968). See Fig. 2 of their paper. The variability of these three stars was announced by Lloyd Evans & Menzies (1971) and confirmed by Lloyd Evans & Menzies (1973). The numbers V6-8 were assigned by Sawyer Hogg in her 3rd (1973) catalogue. -------------------------------------------------------------------- Escobar et al. (2010) conducted a search for stellar variability in this cluster and discovered 54 new variable stars. Among the new variables are 9 RR Lyrae, 7 SX Phe and 18 LPV candidates. Since the cluster lies in a rich field near the Galactic centre, the authors conclude that many of these variables are not cluster members. Their results were presented in a poster paper. Detailed information about the individual variables has not yet been published. ======================================================================== References Catchpole, R. M., Feast, M. W., Menzies, J. W. 1970, Obs, 90, 63 Escobar, M. E., Catelan, M., Zoccali, M., Smith, H. A., Pritzl, B. J., Layden, A., Gregorsok, J., Welch, D. L., Webb, T. 2010, IAUS, 266, 390 Hartwick, F. D. A. & Sandage, A. 1968, ApJ, 153, 715 Heasley, J. N., Janes, K. A., Zinn, R., Demarque, P., Da Costa, G. S., Christian, C. 2000, AJ, 120, 879 Lloyd Evans, T. & Menzies, J. W. 1971, Obs, 91, 1971 Lloyd Evans, T. & Menzies, J. W. 1973, IAU Colloq 21, Variable Stars in Globular Clusters and in Related Systems, 151 Minniti, D. 1995, A&AS, 113, 299 Ponsen, J. 1957, Leiden Ann. 20, 431 Rosino, L. 1962, Mem SAI 33, 351 = Asiago Contr. 132 Samus, N. N., Kazarovets, E. V., Pastukhova, E. N., Tsvetkova, T. M., Durlevich, O. V. 2009, PASP, 121, 1378 Sloan, G. C., Matsunaga, N., Matsuura, M., Zijlstra, A. A., Kraemer, K. E., Wood, P. R., Nieusma, J., Bernard-Salas, J., Devost, D., Houck, J. R. 2010, ApJ, 719, 1274 ======================================================================