NGC 6397 / C1736-536 (Updated January 2015) RA: 17:40:42.09 DEC: -53:40:27.6 (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 17:41:04.75 -53:32:58.2 R0 314.6 13.36 3.94 V M f;Note 2 17:40:10.87 -53:47:33.8 R0 39.5977 12.88 0.47 V RV? f;max;Note 3 17:40:16.88 -53:41:03.6 R0 0.4940 16.07 1.20 V RR0 f;K97 4 17:41:08.71 -53:42:34.6 R0 0.4227 16.35 0.73 V EW max 5 17:41:05.46 -53:33:36.2 R0 0.27 18.70 0.8 V E max;K97 6 17:40:53.24 -53:43:39.8 R0 0.5 17.16 0.13 V EW f;max;K97 7 17:40:43.74 -53:40:35.6 R0 0.2699 17.09 0.47 V EW max 8 17:40:39.14 -53:38:47.1 R0 0.2712 16.24 0.38 V EW max 9 17:40:02.14 -53:35:45.4 R0 0.5802 16.25 0.65 V EW max;K97 10 17:40:37.43 -53:40:36.4 R0 0.0301 15.97 0.12 V SXPHE KT 11 17:40:43.95 -53:40:40.9 R0 0.0383 15.40 0.05 V SXPHE KT 12 17:40:41.42 -53:40:19.6 R0 0.4712 17.52 0.49 V CV? max;Note 13 17:40:48.82 -53:39:49.0 R0 0.2352 19.43 0.47 V CV? max;Note 14 17:40:46.31 -53:41:15.9 R0 0.3351 19.25 0.16 V E max 15 17:40:45.24 -53:40:25.2 R0 0.0215 15.44 0.05 V SXPHE KT 16 17:40:44.44 -53:40:42.0 R0 1.3541 16.65 0.15 V ELL max;Note 17 17:40:43.63 -53:41:16.8 R0 1.061 16.23 0.04 V Ell? 18 17:40:43.45 -53:40:28.1 R0 0.7867 15.75 0.14 V E max 19 17:40:44.66 -53:40:23.8 R0 0.2538 17.12 0.10 V E max 20 17:40:41.51 -53:40:33.7 R0 0.8612 15.83 0.08 V GDOR? 21 17:40:41.40 -53:40:23.9 R0 0.0390 15.48 0.30 V SXPHE KT 22 17:40:41.02 -53:40:42.2 R0 0.344 16.15 0.18 V RR01 23 17:40:39.21 -53:40:46.9 R0 0.0372 15.66 0.04 V SXPHE KT 24 17:40:38.97 -53:40:23.3 R0 0.4570 16.45 0.02 V GDOR? KT 25 17:41:10.16 -53:39:30.5 R0 1.2306 17.98 0.17 V ? 26 17:40:43.05 -53:38:31.2 R0 ---- 16.24 0.09 V ? 27 17:41:13.80 -53:41:14.1 R0 0.5561 18.25 0.05 V Ell? 28 17:41:02.70 -53:39:47.0 R0 25.997 15.13 0.28 V ? 29 17:40:59.64 -53:40:38.6 R0 1.2434 19.72 0.19 V Ell? 30 17:40:54.51 -53:40:44.4 R0 ---- 17.64 0.56 V E f 31 17:40:42.59 -53:40:27.1 R0 1.3100 15.99 0.08 V Ell? 32 17:40:40.30 -53:41:25.2 R0 ---- 16.145 0.03 V E 33 17:40:42.62 -53:40:19.0 R0 ---- 18.3 4.2 V CV? max;Note 34 17:40:42.29 -53:40:28.6 R0 ---- 16.2 5.8 V UG max;Note 35 17:40:43.31 -53:41:55.2 R0 0.2984 18.79 0.17 V Ell 36 17:40:44.10 -53:42:11.3 R0 0.5487 16.53 0.02 V ? PSR see V16 ======================================================================= Supplementary Notes NGC 6397 is a core-collapsed globular cluster with at least 79 Chandra X-ray sources within its half-mass radius. These sources are the subject of numerous investigations. Variability in the optical counterparts of some of these sources has been detected (e.g. V12, V13, V16, V33, V34 in the above table), but investigations continue and more variables may be identified in future. In the above table, the RA and dec are from the following sources: V1 (V639 Ara) and V2 (V825 Ara) from (Samus et al. (2009) V3-V11 (Kaluzny 1997) V12-V24 (Kaluzny & Thompson 2003) V25-V36 (Kaluzny et al. 2006). The remaining data for V3-36 are from Kaluzny et al. (2006) unless indicated otherwise in the Notes/Remarks column where K97 refers to Kaluzny (1997) and KT refers to Kaluzny & Thompson (2003). ===================================================================== Notes on individual stars V1: The membership status of V1 is uncertain. Sawyer (1931), Swope & Greenbaum (1952) and El-Worfaly & Budding (1983) all pointed out that it might belong to the rich field around the cluster and a radial velocity by Feast (1996) indicated that V1 is unlikely to be a cluster member. However, a proper motion study by Cudworth & Benensohn (1994) indicated a fairly high membership probability. The period listed for V1 was published by Sawyer (1931). According to El-Worfaly & Budding (1983), the period might be slightly longer (315.3 days). The V magnitude and ampltude in the above table are from Woolley et al. (1961). V1 is listed in the Moscow GCVS as V639 Ara. V2: The period, magnitudes and classification are from the ASAS survey (Pojmanski & Maciejewski 2004). V2 is considered to be a field star and is listed as V825 Ara in the Moscow GCVS. V12, V13: These are CV1 and CV6 in the list of possible cataclysmic variables detected by Grindlay et al. (2001) with the Chandra telescope. Kaluzny & Thompson (2003) detected periodic variability for these stars in the V band. They attributed this variability to the ellipsoidal effect in a binary system. No outbursts have been observed in either of these variables. V16: This ellipsoidal variable is the optical component of the millisecond pulsar J1740-5340. Photometric variations of this star have been discussed by Kaluzny et al. (2003) and by Orosz & van Kerkwijk (2003). Kaluzny et al. also derived its radial veloctiy and concluded that it is a cluster member. According to Paulo Freire's website, this is the only millisecond pulsar in NGC 6397. (www.naic.edu/~pfreire/GCpsr.html) V33, V34: These are CV3 and CV2 in the list of possible cataclysmic variables detected by Grindlay et al. (2001) with the Chandra telescope. Kaluzny et al. (2006) detected non-periodic variability for these stars in the V band. In V33 (CV3), non-period changes of V exceeding 0.8 mag were observed on some nights. V34 (CV2) exhibited a probable dwarf nova outburst in May 2003 and has therefore been listed as a U Gem star. ==================================================================== Discovery of the variable stars in NGC 6397: V1&2 (=V639 and V825 Ara) Bailey (1902) with x,y coordinates (page 241) and an ID chart (Plate XI, Fig. 2, caption on page 250) Bailey (1923) published data for 4 additional variables in the surrounding field. V3 Swope (unpublished correspondence with Sawyer) The number V3 was assigned by Sawyer (1955) in her 2nd catalogue where she published the x,y coordinates V3 is considered to be a field star and is designated as V826 Ara in the Moscow GCVS. V4-11 Kaluzny (1997) with RA and dec, as well as X,Y pixel numbers that refer to a template image that they submitted to the data centre at Strasburg. V10 is BS#11 that was identified by Lauzeral et al. (1992). El-Worfaly & Budding (1983) discussed and identified a variable which they called V4. It is a different star and is considered to be a field star based on its distance from the cluster. It is listed as V826 Ara in the Moscow GCVS. V12-13 Kaluzny & Thompson (2003) with RA, dec and X,Y pixel numbers that refer to an HST archival image These two variables are the optical counterparts to CV1 and CV6, candidate cataclysmic variables detected by Grindlay et al. (2001) with the Chandra telescope. V14-24 Kaluzny & Thompson (2003) with RA, dec and X,Y pixel numbers that refer to an HST archival image for V14-21. V22 and V23 are BS#8 and BS#16 that were identified by Lauzeral et al. (1992). V25-36 Kaluzny et al. (2006) with RA, dec They published finding charts for most of these variables and for the others (V31, V33 and V34) they cited sources where the charts can be located (see page 549). ------------------------------------------------------ In an investigation to detect planetary transits among low main sequence stars in NGC 6397, Nascimbeni et al. (2012) identified 12 new variable stars. All of them were considered to be field stars, based on the proper motions and position in the CM diagram. ===================================================================== References Alexander et al. 1961, Royal Obs. Bull., 43 Bailey, S. I. 1902, Harv. Ann., 38 Bailey, S. I. 1923, Harv. Bull., 796 Cohn, H. N., Lugger, P. M., Couch, S. M., Anderson J., Cool, A. M., van den Berg, M., Bogdanov, S. and two co-authors, 2010, ApJ, 722, 20 El-Worfaly, H. M. H. & Budding, E. 1983, Ap&SS, 94, 253 Feast, M. W. 1996, Obs., 86, 120 Grindlay, J. E., Heinke, C. O., Edmonds, P. D., Murray, S. S., Cool, A. M. 2001, ApJ, 563, L53 Kaluzny, J. 1997, A&AS, 122, 1 Kaluzny, J,, Rucinski, S. M., Thompson, I. B. 2003, AJ, 125, 1546 Kaluzny, J. & Thompson, I. B. 2003, AJ, 125, 2534 Kaluzny, J., Thompson, I. B., Krzeminski, W., Schwarzenberg-Czerny, A. 2006, MNRAS, 365, 548 Lauzeral, C., Ortolani, S., Auriere, M., Melnick, J. 1992, A&A, 262, 63 Nascimbeni, V., Bedin, L. R., Piotto, G., De Marchi, F., Rich, R. M. 2012, A&A, 541, A144 Orosz, J. A. & van Kerkwijk, M. H. 2003, A&A, 397, 237 Pojmanski, G. & Maciejewski, G. 2004, Acta A., 54, 153 Samus, N. N., Kazarovets, E. V., Pastukhova, E. N., Tsvetkova, T. M., Durlevich, O. V. 2009, PASP, 121, 1378 Sawyer, H. B. 1931, Harv. Circ., 366 Sawyer, H. B. 1955, Publ. DDO, 2, No. 2 Woolley, R.vd. R., Alexander, J. B., Mather, L., Epps, E. 1961, RGO Bull., 43, 303 ======================================================================