NGC 6934 / C2031+072 (Updated September 2018) RA: 20:34:11.37 DEC: +07:24:16.1 (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 20:34:08.4 07:23:39 R0 0.5675 16.80 0.805 V RR0 2 20:34:08.6 07:24:02 R0 0.4819 16.952 1.093 V RR0 3 20:34:11.4 07:25:15 R0 0.5398 16.912 1.072 V RR0 4 20:34:13.9 07:25:15 R0 0.6164 16.775 1.325 V RR0 5 20:34:15.2 07:27:58 R0 0.5646 16.90 0.910 V RR0 6 20:34:09.5 07:23:45 R0 0.5559 16.985 0.932 V RR0 7 20:34:17.4 07:25:16 R0 0.6440 16.872 0.700 V RR0 8 20:34:18.0 07:25:08 R0 0.6240 16.893 0.576 V RR0 9 20:34:15.6 07:24:36 R0 0.5492 16.965 0.967 V RR0 10 20:34:02.2 07:25:28 R0 0.5200 16.94 1.30 V RR0 Kal 11 20:34:12.5 07:24:46 R0 0.3087 16.912 0.553 V RR1 12 20:34:13.2 07:23:34 R0 0.4642 16.95 1.11 V RR0 Note 13 20:34:08.1 07:24:42 R0 0.5513 16.87 1.227 V RR0 14 20:34:10.9 07:22:47 R0 0.5220 16.80 1.162 V RR0 15 20:34:11.9 07:23:25 R0 --- 13.773 0.1 V SR Note 16 20:34:13.7 07:24:36 R0 0.6049 16.896 0.768 V RR0 17 20:34:06.5 07:22:30 R0 0.5983 16.91 0.70 V RR0 Kal 18 20:34:14.6 07:24:09 R0 0.9561 16.50 0.47 V RR? Note 19 20:34:13.2 07:24:19 R0 0.4806 16.645 1.014 V RR0 20 20:34:09.6 07:24:34 R0 0.5483 16.85 1.128 V RR0 21 20:34:08.9 07:24:15 R0 0.5268 16.95 1.051 V RR0 22 20:33:55.3 07:21:24 R0 0.5743 16.93 0.50 V RR0 Kal 23 20:34:09.3 07:24:00 R0 0.2864 16.878 0.560 V RR1 24 20:34:13.8 07:23:24 R0 0.6417 16.949 0.492 V RR0 25 20:34:14.7 07:24:54 R0 0.5091 16.878 1.000 V RR0 26 20:34:13.4 07:21:02 R0 0.2593 16.943 0.431 V RR1 27 20:34:01.4 07:27:39 R0 0.5922 16.88 0.84 V RR0 Kal 28 20:33:55.6 07:25:56 R0 0.4852 16.80 1.260 V RR0 29 20:34:05.7 07:21:14 R0 0.4548 17.04 1.297 V RR0 30 20:34:22.1 07:26:26 R0 0.5899 16.916 0.871 V RR0 31 20:34:21.1 07:22:37 R0 0.5051 16.95 1.20 V RR0 Kal 32 20:34:10.6 07:25:08 R0 0.5119 16.942 1.135 V RR0 33 20:34:13.8 07:24:29 R0 0.5192 16.91 0.87 V RR0 Note 34 20:34:09.9 07:24:32 R0 0.5601 16.991 1.003 V RR0 35 20:34:21.9 07:21:56 R0 0.5442 16.75 1.104 V RR0 36 20:34:12.1 07:23:41 R0 0.4957 16.884 1.181 V RR0 37 20:34:12.9 07:24:28 R0 0.5332 17.009 1.056 V RR0 38 20:34:12.2 07:23:59 R0 0.5236 16.907 1.126 V RR0 39 20:34:11.9 07:24:00 R0 0.5026 16.983 1.212 V RR0 40 20:34:10.7 07:24:44 R0 0.5608 16.81 0.96 V RR0 Kal 41 20:34:13.3 07:23:38 R0 0.5204 16.980 0.957 V RR0 42 20:34:15.0 07:24:39 R0 0.5242 16.869 1.149 V RR0 43 20:34:12.8 07:24:45 R0 0.5632 16.969 0.965 V RR0 44 20:34:08.5 07:23:48 R0 0.6304 16.941 0.505 V RR0 45 20:34:09.2 07:24:08 R0 0.5684 16.80 1.178 V RR0 Note 46 20:34:12.3 07:23:53 R0 0.3286 16.933 0.441 V RR1 47 20:34:12.0 07:23:52 R0 0.6409 16.81 0.48 V RR0 Kal 48 20:34:13.5 07:25:08 R0 0.5613 16.922 0.895 V RR0 49 20:34:12.2 07:23:22 R0 0.2855 16.80 0.50 V RR1 Kal 50 20:34:12.4 07:23:41 R0 0.6345 16.984 0.507 V RR0 51 20:34:11.8 07:24:52 R0 0.5648 16.73 0.80 V RR0 Note 52 20:34:18.3 07:22:14 R0 0.06 18.943 0.471 V SXP Note 53 20:34:13.6 07:24:00 R0 0.2824 16.973 0.600 V RR1 54 20:34:12.6 07:24:35 R0 0.7783 16.750 0.282 V RR0 Note 55 20:34:13.3 07:24:27 R0 0.5902 16.998 0.824 V RR0 Note 56 20:34:12.5 07:24:18 R0 0.2910 16.972 0.597 V RR1 57 20:34:12.4 07:24:10 R0 0.6871 15.839 0.331 V RR0 f?;Note 58 20:34:12.1 07:25:05 R0 0.4008 16.757 0.452 V RR1 59 20:34:12.0 07:24:15 R0 0.5386 16.928 1.125 V RR0 60 20:34:12.0 07:24:56 R0 0.6604 16.895 0.397 V RR0 61 20:34:11.9 07:23:10 R0 ---- 16.890 0.544 V RR Note 62 20:34:11.7 07:24:26 R0 0.5307 16.896 0.715 V RR0 63 20:34:11.6 07:24:26 R0 0.5756 -- -- V RR0 Note 64 20:20:11.4 07:24:18 R0 0.5710 16.555 0.641 V RR0 65 20:34:11.4 07:24:15 R0 0.6591 16.988 1.156 V RR0 66 20:34:11.1 07:24:16 R0 ---- -- -- CST? Note 67 20:34:10.9 07:23:55 R0 0.6133 17.223 0.935 V RR0 68 20:34:10.9 07:24:00 R0 0.3353 16.432 0.520 V RR1 blend 69 20:34:10.8 07:23:15 R0 0.2470 16.925 0.41 V RR1? Note 70 20:34:10.7 07:24:06 R0 0.5393 16.773 0.845 V RR0 71 20:34:10.7 07:23:54 R0 0.5727 16.953 1.041 V RR0 72 20:34:10.5 07:25:20 R0 0.6679 16.885 0.277 V RR0 73 20:34:09.8 07:24:47 R0 ---- 17.01 0.431 V RR Note 74 20:34:09.3 07:24:08 R0 ---- 16.86 1.00 V RR0? Note 75 20:34:02.8 07:19:35 R0 0.2821 17.15 0.36 V EW f;Note 76 20:33:54.6 07:19:50 R0 0.3365 17.94 0.31 V EW f;Note 77 ---- ---- ---- 19.10 -- V L f?;Note 78 20:34:12.1 07:24:38 R0 0.5423 16.492 0.694 V RR0 79 20:34:10.5 07:24:24 R0 0.6219 16.843 0.503 V RR0 Note 80 20:34:11.7 07:24:07 R0 0.5443 16.77 1.0 V RR0 Kal 81 20:34:11.2 07:24:23 R0 0.6 16.92 0.69 V RR0 Note 82 20:34:10.7 07:24:17 R0 0.7311 16.9 -- V RR0 83 20:34:11.2 07:24:26 R0 0.5405 16.70 0.662 V RR0 84 20:34:12.1 07:24:28 R0 0.6654 -- -- RR0 Note 85 20:34:31.0 07:21:57 R0 1.6220 17.46 0.13 V ? f?;Note 86 20:34:19.4 07:22:51 R0 49.0 13.90 0.15 V SR 87 20:34:12.6 07:24:12 R0 0.5747 14.474 0.115 V CW? Note 88 20:34:11.4 07:24:10 R0 0.5196 16.746 1.095 V RR0 89 20:34:11.3 07:24:11 R0 0.5253 17.122 0.999 V RR0 90 20:34:12.4 07:20:53 R0 1.0561 17.005 0.090 V CW? 91 20:34:11.8 07:24:11 R0 0.5471 16.90 0.912 V RR0 92 20:34:05.0 07:25:27 R0 0.0459 19.403 0.12 V SXP 93 20:34:10.1 07:24:11 R0 0.0990 18.638 0.141 V SXP 94 20:34:11.8 07:24:16 R0 0.5733 15.80 0.43 V RR0 f 95 20:34:00.9 07:19:58 R0 0.0243 19.827 -- V SXP 96 20:34:22.2 07:20:10 R0 9.54 13.814 0.1 V SR 97 20:34:16.9 07:20:45 R0 ---- 14.079 -- V SR 98 20:34:23.9 07:27:40 R0 ---- 13.782 -- V SR =================================================================== Supplementary Notes NGC 6934 is an intermediate-metallicity cluster with [Fe/H]=-1.47 according to the 2010 update of the Harris (1996) catalogue. A BV CM diagram by Piotto et al. (1999), based on HST observations, shows a well populated HB with an extended blue HB and a well defined sequence of blue stragglers. Investigations of the variable stars based on CCD data have been carried out by Kaluzny et al. (2001 hereafter Kal01) and by Yepez et al. (2018 - hereafter Yep18). In the above table, the periods for V1-86 are from Kal01 and the remaining data are from Yep18. Exceptions are explained in the notes. In cases where "Kal" is indicated in the remarks column, the magnitudes and amplitudes are from Kal01 because their light curve had better phase coverage. All of the data for V87-98 are from Yep18. =================================================================== Notes on individual stars V12: Yep18 were unable to resolve the light curve for this star because its image was blended with a close neighbour of similar brightness. It was not included in their analysis. The adopted period, magnitude and amplitude are from Kal01. V15: The classification is from Yep18 who showed that V15 is located near the RG tip in the CM diagram. V15 was not studied by Kal01. V18: The period is unusually long for an RR Lyrae variable and its location on the period-amplitude relation is shifted compared with the RR0 variables. Yep18 noted that it is a few tenths of a magnitude brighter than most of the RR Lyrae variables and might be a type II Cepheid. The classification of V18 is uncertain. The mean magnitude and amplitude are from Kal01. V33: The star exhibits the Blazhko effect and consequently the period flucutates. The adopted period is from Sawyer Hogg and Wehlau (1980) and the remaining data are from from Yep18. V45: The period is uncertain because Sawyer Hogg & Wehlau (1980), Kal01 and Yep18 derived significantly different values: 0.568413, 0.53660 and 0.540324 days respectively. A close examination of all of the published light curves for this star indicates that there is some uncertainty in the derived periods. In the above table, the Sawyer Hogg & Wehlau period has been adopted because their observations were more extensive and their value was confirmed by Stagg & Wehlau (1980) in their period change study. V51: Yep18 commented that this star was badly blended in their images. The mean magnitude and amplitude are from Kal01. V52: Both Kal01 and Yep18 classified V52 as SX Phe, but derived slightly different periods: 0.05976 and 0.063563 days respectively. V54, V55: There is some confusion between V54 and V55. The stars that Yep18 listed as V54 and V55 were listed as V55 and V54 respectively by Kal01. The ID chart of Yep18 is consistent with the published coordinates, but the Kal01 finder charts are not. In fact, Samus et al. (2009) already commented on this. In the above table, the numbering system of Yep18 has been used. V57: Kal01 were not able to derive magnitudes for this star, possibly due to blending. Yep18 found that it was about 1 magnitude brighter than the other RR Lyrae variables and concluded that it could be a foreground star. However, if blending is the reason for the apparent brightness, V57 could be a cluster member. It is located at about 15 arcseconds from the cluster centre which is close to the core. Harris (2010) listed a core radius of 13 arcseconds. V61: Kal01 derived a period of 0.528 days for this star but noted that it was very uncertain. There was a lot of scatter on the light curve. Yep18 derived a period of 0.355146 and their light curve is much better. Nevertheless, there are some points on the rising branch that do not fit. According to both studies, its magnitude and colour are similar to those of the other RR Lyrae variables. Therefore it is undoubtedly an RR Lyrae variable but its period and classification are uncertain. V63: No magnitude and amplitude are listed because the minimum light is not well defined on the light curve of Yep18 and Kal01 did not publish any magnitudes. V66: Kal01 published a well defined light curve for this star with P=0.540780, based on differential counts units. However, Yep18 could not detect any variablility in the star at the location published by Kal18. In view of the fact that Kal01 made errors in the identifications of some of the other variables, it seems that the data they published for V66 pertains to a different star, possibly V91 that was later announced by Yep18 and has a similar period. V66 is therefore classified as CST?. V69: Kal01 discussed the possibility that V69 might be pulsating in the second overtone mode. V73: Kal01 derived a period of 0.506 days for this star, but there was considerable scatter on the light curve. Yep18 found that the 0.506 day period could not be fit to their data.  The star is probably a a multi-mode mode pulsator but more observations will be required to establish its true nature. The V-I colour shows the star at the interface between fundamental and first overtone variables in the CMD. V74: Kal01's finder chart for V74 is discrepant. According to their published RA and dec, V74 should be about 1 arcsecond east of V45, but their finder chart indicates a position that is 8 arcseconds south. The Kal01 finder chart for V74 is the same as their chart for V23. Yep18 detected variability in the star at the published postion for V74, but did not have sufficient data to derive a period and the light curve published by Kal01 shows a lot of scatter. Thus the period is uncertain, but the star appears to be a fundamental mode RR Lyrae variable. V75, V76: Kal01 applied a technique devised by Rucinski (2000) for establishing the membership status of EW variables. They concluded that neither of these stars is a cluster member. Samus et al. (2009) noted that they have been listed in the Moscow GCVS as OP Del and OO Del respectively. They also pointed out that the chart for V76 published by Kaluzny et al. (2001) was discrepant. V77, V79: Kal01 published exactly the same coordinates for these two stars. They classified V77 as a long perod variable and V79 as an RR Lyrae. However, their finder charts do not indicate that the stars lie at the same position. Something is wrong. Yep18 found an RR Lyrae variable at the published RA and dec and in the same location as V79, according to the finder chart. Therefore it is assumed that Kal01's published coordinates pertain to V79. It is diffcicult to determine the RA and dec for their V77, based on Kal01's published finder chart. However, if their published magnitudes for V77 are correct, its location on the CM diagram indicates that it is not a cluster member. V81: It is difficult to establish a precise period for V81 because of the Blazhko effect. The period listed above is an approximate value based on the observations of both Kal01 and Yep18. V84: No magnitudes have been listed because the light curves published by both Kal01 and by Yep18 had phase gaps. V85: Kal01 stated that the star was located on the red side of the cluster red giant branch and that a period of 2.606 days was possible. They concluded that further data were needed to establish the type of variability and membership status. Yep18 confirmed the variability of the star and suggested that it might be a type II Cepheid located behind the cluster. V87: This star is about 2 magnitudes above the HB and Yep18 tentatively classified it as a type II Cepheid. However, its published period, 0.57 days seems too short. It might have a longer period or alternatively be a foreground RR Lyrae variable. =================================================================== Discovery of the variable stars in NGC 6934: V1-51 Sawyer, H. B. (1938) with x,y coordinates and an ID chart Preliminary results were announced by Sawyer (1933, 1936) V52-86 Kal01 with RA, dec and individual finder charts However, the orientation of their charts is not north up and east to the left as they claimed in the caption of Fig. 1. A careful examination of many of the individual finder charts indicates that east is to the right, not to the left. Also it has been pointed out by Samus et al. (2009) and by Yep18 that a few of the stars are incorrectly labelled in the finder charts. Therefore the Yep18 ID charts are more useful. V87-98 Yep18 with RA and dec and ID charts They labelled the other known variables on their charts. Yep 18 also identified 5 additional possible variables which they numbered C1 to C5. ==================================================================== References Harris, W. E. 1996, AJ, 112, 1487 Kaluzny, J., Olech, A., Stanek, K. Z. 2001, AJ, 121, 1533 (Kal01) Piotto, G., Zoccali, M., King, I. R., Djorgovski, S. G., Sosin, C., Dorman, B., Rich, R. M., Meylan, G. 1999, AJ, 117, 264 Rucinski, S. M. 2000, AJ, 120, 319 Samus, N. N., Kazarovets, E. V., Pastukhova, E. N., Tsvetkova, T. M., Durlevich, O. V. 2009, PASP, 121, 1378 Sawyer, H. B. 1933, Pub. AAS, 7, 185 Sawyer, H. B. 1936, Pub. AAS, 8, 149 Sawyer, H. B. 1938, Dominion Astrophys. Obs. Publ., 7, 121 Sawyer Hogg, H. & Wehlau, A. 1980, AJ, 85, 148 Stagg, C., Wehlau, A. 1980, AJ, 85, 1182 Yepez, M. A., Arellano Ferro, A., Muneer, S., Giridhar, S. 2018, Rev. Mex. A&A, 54, 15; erratum 2018, Rev. Mex. A&A, 54, 501 (Yep18) =====================================================================