NGC 6652 / C1832-330
RA: 18:35:45.63 DEC: -32:59:26.6  (J2000)

(Most recent updates: 
Membership probability flag - 2024; Remaining data - January 2015)
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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        18 35 41.43 -32 55 47.5 u  ----     18.5   1.2   B ?
2        18 35 26.79 -32 54 31.3 u  ----     14.65  --    B L     amp>2.7
3        18 35 19.10 -32 58 56.8 u    0.52   18.2   1.6   B RR0   f?            
4        18 35 31.76 -32 54 54.6 u  ----     18.35  0.7   B ?     Note
5        18 35 45.47 -33 05 00.6 u    0.67   16.1   0.6   B RR0   f?            
6        18 35 27.39 -32 59 04.1 u    0.259  17.1   0.6   B RR1   f?            
7        18 35 32.99 -32 57 23.3 u  ----     15.6   --    B SR    Note
8        18 36 11.83 -33 02 21.2 u  ----     16.4   --    B E?    max
9        18 36 19.84 -32 56 40.6 u    0.63   15.9   1.4   B RR0   f?;Note 
10       18 35 43.65 -32 59 26.8 m1 ----     18.9   --    V LMXB 
11       18:35:44.57 -32:59:38.3 f  ----     18.72  1.09  I qLMXB Note
12       18:35:45.75 -32:59:23.5 f  ----     20.5   --    V CV?
13       18:35:45.81 -32:59:35.9 m1 ----     14.17  0.04  I ?  
14       18:35:46.33 -32:59:32.8 f    0.1898 17.74  0.29  I EW?   RR?  

PSR      -- -- --     -- -- --   u ----     --     --            2 msPs
============================================================================
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 at the Max Planck 
        Institute in Bonn (July 2024 version), there are 
        2 millisecond pulsars in NGC 6652.
------------------------------------------------------------------------
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

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

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

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
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