NGC 6366 / C1725-050 (Updated April 2014) RA: 17:27:44.24 DEC: -05:04:47.5 (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 17:27:42.69 -05:05:25.2 R0 0.5132 15.806 0.82 V RR0 Note 2 17:28:04.65 -05:11:13.9 R0 ---- 15.022 -- V SR f?;Note 3 17:28:00.09 -05:06:51.9 R0 3.7238 14.29 0.13 V CW? f?;Note 4 17:27:45.26 -05:05:42.9 R0 ---- 16.62 -- V L? RGB;Note 5 17:27:24.98 -05:01:05.8 R0 ---- 16.31 -- V L? RGB;Note 6 17:27:56.65 -05:08:32.9 R0 0.0802 16.98 0.047 V SXPHE 7 17:27:48.26 -05:08:20.1 R0 ---- 17.09 -- V L? RGB;Note 8 17:27:39.15 -05:03:01.8 R0 0.7429 18.70 0.15 V E ==================================================================== Supplementary Notes The RA and dec for V1 and V2 are from Lloyd et al. (2008). The RA and dec for V3-8 were derived by Arellano Ferro (2014 - private communication) by locating their images in the ALADIN sky atlas. The remaining data for V3-8 are from Arellano Ferro et al. (2008). ============ Notes on individual variables V1: The period, mean V magnitude, amplitude and RR0 classification are from Arellano Ferro et al. (2008) who argued that the star might be a field star, more distant than the cluster. V2: The V magnitude is from Harris (1993) who also derived (B-V) = 2.218. The SR classification is from Lloyd et al. (2008) who analysed the Sawyer Hogg data. They thought it likely that the star lies below the giant branch and therefore might not be a cluster member. V2 was outside the field of view in the Arellano Ferro et al. (2008) study. V3: Arellano Ferro et al. (2008) noted that this variable could be either a type II Cepheid or an anomalous Cepheid, but also commented that the possibility that V3 is not a cluster member can not be ruled out. V4, V5, V7: These 3 stars, all on the RGB, have properties similar to Omega Centauri variables V216 and V234 (Ogle #22 and #31) which were initially classified as probable RS CVn type variables by Kaluzny et al. (1996) in their discovery paper. However, in a later paper (Kaluzny et al. 2004), they revised the classification to "LT". =================================================================== Discovery of the variable stars in NGC 6366: V1-2 Sawyer (1940) with x,y positions and ID chart V3-8 Arellano Ferro et al. (2008) with positions labelled on an ID chart. The RA and dec were later derived by Arellano Ferro (2014- private communication). These authors also identified a number of candidate variables: C1-C7 - possible long period variables or Cepheids - the timing of their observations was not suitable for confirming this. C8-11 - short period variables that could be eclipsing binaries of the W UMa type. ==================================================================== Additional candidate variables Bassa et al. (2008) identified 5 X-ray sources within the half mass radius, based on Chandra data. They concluded that the brightest source CX1 (a point source surrounded by an extended source) is an old nova. They also found optical counterparts in the cluster for CX4 and CX5, which could be magnetically active binaries. The CM diagrams of Harris (1993) and Sarajedini et al. (2007) show a large blue straggler (BS) population, but the only BS variable detected so far is the SX Phe star V6 (Arellano Ferro et al. 2008). ==================================================================== References Arellano Ferro, A., Giridhar, S., Rojas Lopez, V., Figuera, R., Bramich, D. M., Rozenzweig, P. 2008, Rev. Mex. A&A 44, 365 Bassa, C. G., Pooley, D., Verbunt, F., Homer, L., Anderson, S. F., Lewin, W. H. G. 2008, A&A, 488, 921 Harris, H. C. 1993, AJ, 106, 604 Kaluzny, J., Kubiak, M., Szymanski, M., Udalski, A., Krzeminski, W., Mateo, M. 1996, A&AS, 120, 139 Kaluzny, J., Olech, A., Thompson, I. B., Pych, W., Krzeminski, W., Schwarzenberg-Czerny, A. 2004, A&A, 424, 1101 Lloyd, C., Pike, C. D., Terzan, A., Sawyer Hogg, H. B. 2008, Obs., 128, 280 Sarajedini, A., Bedin, L. R., Chaboyer, B., Dotter, A., Siegel, M., Anderson, J., Aparicio, A. and 6 coauthors, 2007, AJ, 133, 1658 Sawyer, H. B. 1940, Publ. DDO, 1, No. 5 ======================================================================