NGC 6864 / C2003-220 / Messier 75
RA: 20:06:04.69  DEC: -21:55:16.2  (J2000)

(Most recent updates: 
Membership probability flag - 2024; Remaining data - August 2014)
============================================================
Bytes  Format      Explanation
1-8      A8        Star ID
10-32  A11,1x,A11  Position
34-35    A2        Membership probability flag based on data published
                   by Prudil & Arellano Ferro (2024)
                    m1: prob >=0.85;  m2: prob >=0.7 and <0.85;
                    m3: prob >= 0.5 and <0.7; f: prob <0.5
                    u:  no data available
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               Mem   Period <mag>  ampl  C Type  Notes/
         RA          Dec        Flag                              Remarks
=========================================================================
1        20:06:06.0  -21:56:43   m1   0.5901 --     --      RR0   
2        20:06:03.95 -21:54:14.1 f  ----     17.1   0.4   B SR    PRC
3        20:06:06.25 -21:53:51.0 m3   0.5451 17.810 0.73  V RR0   
4        20:06:03.68 -21:56:45.1 f    0.2847 17.683 0.57  V RR1   
5        20:06:12.62 -21:54:43.0 m1 ----     --     --      CST
6        20:06:05.40 -21:56:40.9 m1 ----     --     --      CST
7        20:06:02.84 -21:54:00.0 m1 ----     --     --      CST
8        20:06:03.95 -21:55:59.3 m1   0.8398 17.432 0.60  V RR0   Note
9        20:06:08.1  -21:55:44   m1   0.3492 17.729 0.63  V RR1   
10       20:06:01.7  -21:54:27   m1 ----     --     --      CST
11       20:05:56.13 -21:53:53.4 m1   0.2563 17.851 0.41  V RR1   
12       20:06:07.54 -21:54:02.0 m1   0.2706 17.848 0.54  V RR1   
13       20:06:14.23 -21:56:18.2 m1   0.4924 17.756 1.30  V RR0   
14       20:06:07.66 -21:55:22.2 f    0.5758 --     --      RR0
15       20:06:00.29 -21:55:16.8 m1 ----     --     --      CST
16       20:06:02.73 -21:54:21.1 m1 ----     16.9   0.6   B SR    PRC
17       20:06:00.14 -21:55:12.7 m1 ----     16.95  0.5   B SR    PRC   
18       20:06:04.25 -21:54:21.8 m1   0.5656 --     --      RR0   
19       20:06:04.98 -21:54:38.8 m3   0.5677 17.633 1.14  V RR0  
20       20:06:04.40 -21:54:53.4 m1   0.5136 17.571 1.34  V RR0   
21       20:06:02.96 -21:55:09.8 m1   0.2566 --     --      RR1   
22       20:06:05.65 -21:55:35.9 m1   0.5144 --     --      RR0   
23       20:06:06.06 -21:55:38.9 m1   0.6122 17.742 0.73  V RR0   
24       20:06:03.68 -21:55:41.8 m1   0.5349 17.665 0.86  V RR0   
25       20:06:05.32 -21:55:44.4 m2   0.3776 16.964 0.30  V RR1   
26       20:06:06.90 -21:55:54.8 m1   0.5421 --     --      RR0   
27       20:06:02.82 -21:56:10.8 m1   0.6503 17.797 0.54  V RR0   Note
28       20:06:02.46 -21:55:59.8 m1   0.2930 --     --      RR1   
29       20:06:08.33 -21:55:00.5 m1   0.3536 17.752 0.50  V RR1   
30       20:06:06.34 -21:55:05.4 m1   0.6834 --     --    V RR0   
31       20:06:06.04 -21:55:15.1 f    0.2662 --     --      RR1   
32       20:06:05.38 -21:55:22.5 m1   0.6262 --     --      RR0   
33       20:06:04.97 -21:55:25.0 u    0.5651 --     --      RR0 
34       20:06:04.18 -21:55:45.8 m1   0.4724 --     --      RR0   
35       20:06:04.15 -21:55:13.9 f    0.5673 --     --      RR0   
36       20:06:04.03 -21:55:22.3 m1   0.3739 --     --      RR1   
37       20:06:03.71 -21:55:18.9 m1   0.5969 --     --      RR0   
38       20:06:03.69 -21:55:21.5 f    0.5304 --     --      RR0   
39       20:06:04.89 -21:55:12.3 m1   0.6273 --     --      RR0   
40       20:06:04.64 -21:55:10.4 m2   0.5511 --     --      RR0   
41       20:06:04.58 -21:55:29.7 u    0.6468 --     --      RR0   
42       20:06:04.88 -21:55:31.3 m1   0.5967 --     --      RR0   
43       20:06:04.94 -21:55:15.5 u    0.2960 --     --      RR1   
44       20:06:08.04 -21:56:30.8 m1   0.6630 17.809 0.25  V RR0   
45       20:06:06.02 -21:55:48.6 m1   0.2511 17.666 0.13  V RR1   
46       20:06:04.16 -21:55:12.2 f    0.3415 --     --      RR1?  
47       20:06:04.04 -21:55:23.8 m1   0.5642 --     --      ?    
48       20:06:05.36 -21:55:19.9 m3   0.278  --     --      RR1? 
49       20:06:05.19 -21:55:15.5 m1   0.276  --     --      RR1?  blend?
50       20:06:04.90 -21:55:16.8 m1   0.634  --     --      EB?   
51       20:06:04.79 -21:55:16.6 m1   0.269  --     --      RR1? 
==========================================================================
Supplementary Notes 

Note that V18-47 are NV1-30 of Corwin et al. (2003) and V48-51 are NV1-4
of Scott et al. (2006).

The RA and dec for V1-17 are from Samus et al. (2009).  
The RA and dec for most of the other stars were supplied by Rodrigo 
Contreras (2012, private communication) from the investigation by 
Contreras et al.  (2012).  
The exceptions were V21, V24, V27, V28, V34 and V47-51. For these stars, 
the RA and dec were calculated from the x,y positions published 
by Corwin et al. (2003) and Scott et al. (2006).  For these calculations, 
it was assumed that the origin of their x,y system was RA=20:06:04.90 and 
dec=-21:55:17.8. Making this assumption gave good agreement with the
coordinates Contreras et al. derived for the other stars.

All of the remaining data for V1-47 are from Corwin et al. (2003) unless 
indicated by PRC in the remarks column, in which case they are from Pinto 
et al. (1982).  Corwin et al. did not derive magnitudes and amplitudes
for all of the variables because they used the image subtraction technique 
for their analysis.  They observed in B and V, but only V magnitudes are 
listed here.
All of the data for V48-51 are from Scott et al. (2006). 

Contreras et al (2012) identified 62 blue straggler stars which are
highly segregated in the cluster core. They published their RA, dec and 
magnitudes.  Some of these are probably variable, but their data were
not suitable for carrying out a variable star search. However, the
position of their star BSS#5, RA=301.5202849 and dec -21.9213937, seems
to be close to the suspected binary V50 (NV4 of Scott et al. 2006).
=========================================================================
Notes on individual stars

V8,V27:

   The x,y coordinates (-14, -40) that Corwin et al. listed for their NV10  
   are very close to the values Shapley (1920) published for V8 
   (-13.5, -41.4), but Corwin et al. listed  (-29, -53) for V8.
   Thus in the above table, Corwin's NV10 is V8 and the star that Corwin
   et al. listed as V8 is V27.
=====================================================================
Discovery of the variable stars in NGC 6864:

V1-12
   Shapley (1920) with x,y coordinates and an ID chart
   He also announced suspected variables V13-16, but Sawyer Hogg did 
   not include these four stars in any of her catalogues. Shapley's
   V13-16 were referred to as S1-4 by Pinto et al. (1982) and also 
   by Samus et al. (2009) who derived their RA and dec. Pinto et al. 
   noted that they were probably not variable and this result was 
   confirmed by Corwin et al. (2003).

V13-17
   Pinto et al. (1982) with x,y coordinates and an ID chart

V18-47  = Corwin NV1-NV30
   Corwin et al (2003) with x,y coordinates

V48-51  = Scott NV1-NV4
   Scott et al. (2006)  with x,y coordinates

============================================================
References

Contreras Ramos, R., Ferraro, F. R., Dalessandro, E., Lanzoni, B., Rood,
R. T. 2012, ApJ, 748, 91

Corwin, T. M., Catelan, M., Smith, H. A., Borissova, J., Ferraro, F. R.,
Raburn, W. S. 2003, AJ, 125, 2543 

Pinto, G., Rosino, L., Clement, C. M.  1982, AJ, 87, 635 

Prudil Z., Arellano Ferro, A. 2024, MNRAS, 534, 3654

Samus, N. N., Kazarovets, E. V., Pastukhova, E. N., Tsvetkova, T. M.,
Durlevich, O. V. 2009, PASP, 121, 1378

Scott, N. J., Corwin, T. M., Catelan, M., Smith, H. A. 2006, IBVS, 5706 

Shapley, H. 1920, ApJ, 52, 73 
=======================================================================