NGC 6401 / C1735-238 (Updated March 2017) RA: 17:38:36.93 DEC: -23:54:31.5 (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, 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 17:38:37.23 -23:54:01.9 R0 ---- 14.96 0.40 CST? Note 2 17:38:33.97 -23:54:26.6 R0 0.7016 17.66 0.93 V RR0 3 17:38:41.31 -23:54:34.9 R0 1.7487 16.41 -- V CWB 4 17:38:36.36 -23:54:35.2 R0 0.4723 1.18 V RR0 5 17:38:34.01 -23:54:40.8 R0 0.5329 18.23 1.19 V RR0 6 17:38:38.19 -23:53:58.2 R0 0.4445 17.96 1.55 V RR0 7 17:38:40.99 -23:54:32.3 R0 0.5456 17.60 1.19 V RR0 8 17:38:38.72 -23:55:25.0 R0 0.3249 17.71 0.54 V RR1 9 17:38:36.76 -23:54:39.2 R0 0.5137 17.51 1.15 V RR0 10 17:38:38.57 -23:53:52.4 R0 0.5260 17.88 1.32 V RR0 11 17:38:40.82 -23:54:08.2 R0 0.5821 17.59 0.90 V RR0 12 17:38:35.09 -23:54:30.8 R0 0.2913 17.23 0.67 V RR1 Note 13 17:38:35.63 -23:54:49.0 R0 0.5650 18.04 1.13 V RR0 14 17:38:39.37 -23:54:39.0 R0 0.6085 17.58 0.54 V RR0 15 17:38:37.78 -23:55:09.5 R0 0.5044 17.84 1.30 V RR0 16 17:38:36.00 -23:55:58.1 R0 0.5058 18.51 1.27 V RR0 17 17:38:41.67 -23:52:57.0 R0 0.5052 17.22 1.34 V RR0 18 17:38:33.84 -23:54:03.8 R0 0.5683 17.71 1.25 V RR0 19 17:38:43.80 -23:56:12.1 R0 0.5599 17.63 1.06 V RR0 20 17:38:36.0 -23:54:31 R0 ---- -- -- CST? Note 21 17:38:36.77 -23:54:12.2 R0 0.2781 17.86 0.52 V RR1 22 17:38:34.87 -23:54:40.6 R0 0.2997 17.98 0.50 V RR1 23 17:38:39.91 -23:52:27.2 R0 0.3664 17.28 0.51 V RR1 24 17:38:45.53 -23:53:54.8 R0 0.5200 17.65 1.05 V RR0 25 17:38:36.27 -23:55:03.0 R0 0.5587 17.55 0.71 V RR0 26 17:38:28.16 -23:54:24.2 R0 0.4959 18.22 1.16 V RR0 27 17:38:33.01 -23:55:04.8 R0 0.2874 18.40 0.55 V RR1 28 17:38:33.56 -23:56:52.8 R0 0.6258 18.00 0.54 V RR0 29 17:38:34.16 -23:55:07.2 R0 0.2886 18.34 0.55 V RR1 30 17:38:34.79 -23:55:05.0 R0 0.2620 18.07 0.42 V RR1 31 17:38:34.87 -23:54:35.6 R0 0.5771 18.00 0.91 V RR0 32 17:38:35.65 -23:54:51.8 R0 0.6614 17.94 0.68 V RR0 33 17:38:35.70 -23:55:26.3 R0 0.3403 18.13 0.50 V RR1 34 17:38:36.79 -23:54:35.4 R0 0.5444 17.60 0.90 V RR0 35 17:38:37.00 -23:54:35.5 R0 0.2828 17.05 0.31 V RR1 36 17:38:42.86 -23:52:57.3 R0 0.3190 17.76 0.44 V RR1 37 17:38:43.06 -23:52:35.3 R0 0.4792 17.93 1.38 V RR0 38 17:38:41.02 -23:56:26.6 R0 ---- -- -- L 39 17:38:36.35 -23:54:20.5 R0 ---- -- -- L 40 17:38:41.74 -23:54:22.4 R0 ---- -- -- L 41 17:38:27.34 -23:53:46.7 R0 0.5874 19.824 0.380 V EC max 42 17:38:27.70 -23:55:10.9 R0 0.7369 - 0.821 V E max 43 17:38:29.78 -23:54:02.6 R0 0.3970 19.438 0.418 V EC max 44 17:38:32.38 -23:53:07.4 R0 0.4244 20.230 0.174 V E max 45 17:38:33.83 -23:53:44.0 R0 0.6332 20.540 0.503 V E max 46 17:38:34.26 -23:53:31.7 R0 7.0321 20.223 0.660 V E max 47 17:38:34.86 -23:55:08.8 R0 1.1673 19.477 0.724 V E max 48 17:38:35.34 -23:53:54.7 R0 0.3569 20.989 0.453 V E max 49 17:38:36.18 -23:55:35.9 R0 0.4969 21.362 0.610 V EC max 50 17:38:41.32 -23:54:06.8 R0 0.4731 20.361 0.567 V EC max 51 17:38:42.01 -23:54:43.1 R0 0.5303 19.207 0.145 V E max 52 17:38:42.33 -23:54:44.1 R0 0.4656 20.161 0.390 V E max 53 17:38:44.53 -23:56:01.6 R0 0.4397 20.229 0.300 V EC max 54 17:38:46.36 -23:54:21.3 R0 0.4121 20.623 0.510 V EC max ====================================================================== Supplementary Notes NGC 6401 is located in a rich, heavily reddened field in the Galactic bulge. This is illustrated in a VI CM diagram published by Barbuy et al. (1999). It is very "noisy" due to differential reddening and contamination from field stars. Nevertheless, Barbuy et al. concluded that the cluster has a red HB. The most comprehensive investigation of the variable stars in NGC 6401 was by Tsapras et al. (2017) who searched for variables in a 15.8 by 15.8 arcminute field centred on the cluster - down to a limiting magnitude of V~19.5 mag. The field around the cluster was also included in the OGLE IV Galactic Bulge survey. Results have been published for RR Lyrae variables (Soszynski et al. 2014) and for eclipsing binaries (Soszynski et al. 2016). The core radius and tidal radius listed by Harris (2010) are 0.25 and 12.24 arcminutes respectively. However, it is unlikely that all the stars within the tidal radius are cluster members. In the above table, only stars within 2.4 arcminutes of the cluster centre are included. This was the NGC 6401 radius listed by Soszynski et al. (2014) and the radius adopted by Tsapras et al. (2017) for their investigation as well. V1-40: The data in the above table are from Tsapras et al. (2017), unless indicated otherwise in the notes on individual stars. Most of these stars were also included in the OGLE IV survey. Tsapras et al. (2017) listed the OGLE numbers in their tables. V41-54: All of these stars are eclipsing binaries and the data are from the OGLE IV survey (Soszynski et al. 2016). In stars for which two eclipses were observed, the amplitudes refer to the primary eclipses. ====================================================================== Notes on individual stars V1: The chart published by Terzan & Rutily (1975) indicates that V1 has a nearby companion and its image is not resolved. Since its variability was not detected by Soszynski et al. (2014) or by Tsapras et al. (2017), it is unlikely that it is variable. The RA and dec are from Samus et al. (2009). V12: This star has two periods, 0.291 and 0.2575 days, respectively. Soszynski et al. (2014 - OGLE IV) interpreted this as two first overtone RR Lyrae variables along the line of sight. On the other hand, Tsapras et al. (2017) concluded that it is a single star pulsating in two modes, at least one of which is non-radial. V20: The chart published by Terzan & Rutily (1975) indicates that the star is located in the crowded central region where its image is not resolved. Since its variability was not detected by Soszynski et al. (2014) or by Tsapras et al. (2017), it is unlikely that V20 is variable. The RA and dec are from Samus et al. (2009). ====================================================================== Discovery of the variable stars in NGC 6401: V1 = star #41 of Terzan & Rutily (1972) who published 1950 RA & dec and an ID chart. It is also NSV 09335 in the GCVS. The number V1 was assigned by Sawyer Hogg (1973). In their discovery paper, Terzan & Rutily announced the discovery of 102 variables, but most were considered to belong to the rich field surrounding the cluster. V2-3 = stars #157 and #164 of Terzan & Rutily (1973) who published 1950 RA & dec and an ID chart The numbers V2-3 were assigned by Sawyer Hogg (1973). In their paper, Terzan & Rutily announced the discovery of 115 variables which they numbered #103 to #217. Most were considered to belong to the rich field surrounding the cluster. V4-25 Terzan & Rutily (1975) with x,y coordinates and an ID chart On the chart, these stars were labelled #218 to #239 respectively. and the other variables (V1, 2, 3 = stars #41, 157 and 164) were also labelled. No magnitudes or periods were published. V26-37 Tsapras et al. (2017) with RA, dec, ID chart and individual finder charts These are all RR Lyrae variables that are located within 2.4 arcminutes of the cluster centre (the radius designated by Soszynski et al. 2014). Tsapras et al. also published data for 17 additional RR Lyrae that were located beyond 2.4 arcminutes. On the OGLE IV website (Soszynski et al. 2014), data are listed for 33 RR Lyrae variables located at distances between 2.4 arcminutes and the tidal radius (12.24 arcminutes). V38-40 (=LPV1, LPV3, LPV12) Tsapras et al. (2017) with RA, dec, ID chart and individual finder charts The numbers V38-40 have been assigned in this catalogue. Tsapras et al. discovered 12 long period variables (LPV1-12), but only these three are located within 2.4 arcminutes of the cluster centre, their designated cluster radius. V41-54 V41 = OGLE-BLG-ECL-051686, V42 = OGLE-BLG-ECL-051718 V43 = OGLE-BLG-ECL-051888, V44 = OGLE-BLG-ECL-052111 V45 = OGLE-BLG-ECL-052212, V46 = OGLE-BLG-ECL-052246 V47 = OGLE-BLG-ECL-052291, V48 = OGLE-BLG-ECL-052324 V49 = OGLE-BLG-ECL-052388, V50 = OGLE-BLG-ECL-052772 V51 = OGLE-BLG-ECL-052829, V52 = OGLE-BLG-ECL-052850 V53 = OGLE-BLG-ECL-052984, V54 = OGLE-BLG-ECL-053107 Soszynski et al. (2016) with RA and dec (OGLE IV Galactic Bulge survey) The numbers V41-54 have been assigned in this catalogue. These 14 binary systems are located within 2.4 arcminutes of the cluster centre, the radius that Soszynski et al. (2014) listed for NGC 6401. (They were all to faint to be detected by Tsapras et al.) In addition to these 14 stars, the OGLE IV website lists data for 333 other eclipsing binaries that are located within the tidal radius of NGC 6401 (12.24 arcminutes). ====================================================================== References Barbuy, B., Ortolani, S., Bica, E., Desidera, S. 1999, A&A, 348, 783 Harris, W. E. 2010, arXiv:1012.3224 Samus, N. N., Kazarovets, E. V., Pastukhova, E. N., Tsvetkova, T. M., Durlevich, O. V. 2009, PASP, 121, 1378 Sawyer Hogg, H. 1973, Publ. DDO, 3, No. 6 Soszynski, I., Pawlak, M., Pietukowicz, P., Udalski, A., Szymanski, M. K., Wyrzykowski, L., Ulaczyk, K. and 6 coauthors, 2016, Ac. A., 66, 405 (Ogle IV Bulge Eclipsing Binary Systems) Soszynski, I., Udalski, A., Szymanski, M. K., Pietukowicz, P. , Mroz, P., Skowron, J., Kozlowski, S. and 6 coauthors, 2014, Ac. A., 64, 177 (Ogle IV Bulge RR Lyrae) Terzan, A. & Rutily, B. 1972, A&A, 16, 408 Terzan, A. & Rutily, B. 1973, IAU Colloq. No. 21, Variable Stars in Globular Clusters and in Related Systems, 68 Terzan, A. & Rutily, B. 1975, A&A, 38, 307 Tsapras, Y., Arellano Ferro, A., Bramich, D. M., Figuera Jaimes, R., Kains, N., Street, R., Hundertmark, M. and 3 coauthors, 2017, MNRAS, 465, 2489 =====================================================================