NGC 6652 / C1832-330 (Updated January 2015) RA: 18:35:45.63 DEC: -32:59:26.6 (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 35 41.43 -32 55 47.5 R0 ---- 18.5 1.2 B ? 2 18 35 26.79 -32 54 31.3 R0 ---- 14.65 -- B L amp>2.7 3 18 35 19.10 -32 58 56.8 R0 0.52 18.2 1.6 B RR0 f? 4 18 35 31.76 -32 54 54.6 R0 ---- 18.35 0.7 B ? Note 5 18 35 45.47 -33 05 00.6 R0 0.67 16.1 0.6 B RR0 f? 6 18 35 27.39 -32 59 04.1 R0 0.259 17.1 0.6 B RR1 f? 7 18 35 32.99 -32 57 23.3 R0 ---- 15.6 -- B SR Note 8 18 36 11.83 -33 02 21.2 R0 ---- 16.4 -- B E? max 9 18 36 19.84 -32 56 40.6 R0 0.63 15.9 1.4 B RR0 f?;Note 10 18 35 43.65 -32 59 26.8 R0 ---- 18.9 -- V LMXB 11 18:35:44.57 -32:59:38.3 R0 ---- 18.72 1.09 I qLMXB Note 12 18:35:45.75 -32:59:23.5 R0 ---- 20.5 -- V CV? 13 18:35:45.81 -32:59:35.9 R0 ---- 14.17 0.04 I ? 14 18:35:46.33 -32:59:32.8 R0 0.1898 17.74 0.29 I EW? RR? PSR-A -- -- ---- -- -- PSR ============================================================================ Supplementary Notes A BV CM diagram by Ortolani et al. (1994) shows a red HB and a well populated blue straggler sequence. The RA and dec for V1-9 and V11 are from Samus et al. (2009). The remaining data for V1-9 are from the discovery paper by Hazen (1989). The data for V10 and V12 are from Heinke et al. (2001). The data for V13 and 14 are from Skottfelt et al. (2015). ============================================================================ Notes on individual stars V4: Hazen (1989) could not derive any period in the range 0.2 to 3 days that gave a good fit. There was a suggestion of periodicity at 0.47 and 1.2 days. V7, V9: According to Samus et al. (2009), these are V3616 Sgr and V3641 Sgr in the GCVS. They were previously studied by Plaut (1971) and were #1243 and #1272 in the Plaut catalogue. Plaut classified #1243 as SR. and derived P=0.62644 for the RR Lyrae variable #1272. The data in the above table are from Hazen (1989). V11: Heinke et al. (2001) classified this system as a qLMXB, but Stacey et al. (2012) suggested it might a VFXT (very faint X-ray transient). The magnitude and amplitude are from Skottfelt et al. (2015). Engel et al. (2012) found a highly variable light curve in the V band with strong magnitude fluctuations (up to 1 mag) on time scales of 5 to 20 minutes. ============================================================================ Discovery of the variable stars in NGC 6652: V1-9 Hazen (1989) with x,y coordinates and ID chart Hazen also provided data for an additional 15 variables outside the cluster tidal radius which was considered at the time to be 466 arcsec. V10 = Optical counterpart of X-ray source A Heinke et al. (2001) with RA, dec for source A and Chandra X-ray image for sources A-C with optical counterparts superimposed. Engel et al. (2012) derived a 2.15 hour orbital period for the binary. V11 = optical counterpart of X-ray source B = star 49 of Deutsch et al. (1998) who published an ID chart The optical variability was first detected by Deutsch et al. (2000) who concluded it was the optical counterpart of the strong X-ray source (now referred to as source A) in NGC 6652. However, Heinke et al. (2001) subsequently showed that Deutsch's star 49 was associated with X-ray source B, not source A. In the electronic catalogue by Clement et al. (2001), star 49 was initially assigned the number V10 and Samus et al. (2009) derived its RA and dec. V10 is now considered to be the variable star associated with X-ray source A. V12 = Optical counterpart of X-ray source C Heinke et al. (2001) with RA, dec for source C and Chandra X-ray image for sources A-C with optical counterparts superimposed. V13-14 Skottfelt et al. (2015) with RA, dec and a finding chart V13 exhibited an outburst in the course of their observations and is probably the optical counterpart of X-ray source H. PSR: According to Paulo Freire's website: www.naic.edu/~pfreire/GCpsr.html a millisecond pulsar in NGC 6652 was discovered by DeCesar et al. (2011). ------------------------------------------------------------------------ In an analysis of Chandra X-ray sources in NGC 6652, Stacey et al. (2012) discussed the properties of 12 X-ray sources (A-L). Four of these sources (A, B, C, and H) are listed as V10-13 in the above table because they have all been detected as optical variable stars. ======================================================================== References Clement, C. M., Muzzin, A., Dufton, Q., Ponnampalam, T., Wang, J., Burford, J., Richardson, A., Rosebery, T. 2001, AJ, 122, 2587 DeCesar, M. E., Ransom, S. M., Ray, P. S. 2011, arXiv:1111.0365 Deutsch, E. W., Margon, B., Anderson, S. F. 1998, AJ, 116, 1301 Deutsch, E. W., Margon, B., Anderson, S. F. 2000, ApJ, 530, L21 Engel, M. C., Heinke, C. O., Sivakoff, G. R., Elshamouty, K. G., Edmonds, P. D. 2012, ApJ, 747, 119 Hazen, M. L. 1989, AJ, 97, 771 Heinke, C. O., Edmonds, P. D., Grindlay, J. E. 2001, ApJ, 562, 363 Ortolani, S., Bica, E., Barbuy, B. 1994, A&A, 286, 444 Plaut, L. 1971, A&AS, 4, 75 Samus, N. N., Kazarovets, E. V., Pastukhova, E. N., Tsvetkova, T. M., Durlevich, O. V. 2009, PASP, 121, 1378 Skottfelt, J., Bramich, D. M., Figuera Jaimes, R., Jorgensen, U. G., Kains, N., Arellano Ferro, A., Alsubai, K. A. and 27 coauthors, 2015, A&A, 573, A103 Stacey, W. S., Heinke, C. O., Cohn, H. N., Lugger, P. M., Bahramian, A. 2012, ApJ, 751, 62 ============================================================================