Palomar 2 / C0443+313
RA: 04:46:05.91  DEC: +31:22:53.4 (J2000)

(Most recent updates: 
Membership probability flag - 2024; Remaining data - June 2024)
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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        04:46:03.57 +31:22:45.8 m1   0.5428 20.534 0.805 V RR0
2        04:46:04.60 +31:23:41.5 m1   0.5514 21.342 1.056 V RR0
3        04:46:05.53 +31:23:29.0 m1   0.5544 21.792 0.951 V RR0
4        04:46:05.61 +31:23:43.2 m1   0.6519 21.413 0.814 V RR0
5        04:46:07.02 +31:23:13.5 m1   0.5116 21.382 0.997 V RR0
6        04:46:07.82 +31:23:07.7 m1   0.5533 21.461 1.168 V RR0
7        04:46:08.11 +31:23:37.1 m1   0.6558 20.925 0.914 V RR0
8        04:46:08.06 +31:22:21.7 m1   0.3734 20.757 0.548 V RR1
9        04:46:08.24 +31:23:09.3 m1   0.6296 21.521 0.787 V RR0
10       04:46:09.11 +31:22:38.0 m1   0.6859 20.700 0.512 V RR0
11       04:46:10.58 +31:22:35.0 m1   0.5753 20.673 0.842 V RR0
12       04:46:12.82 +31:22:26.3 m1   0.5836 20.894 0.603 V RR0
13       04:46:07.17 +31:23:15.5 m1   0.5470 21.327 0.887 V RR0
14       04:46:07.21 +31:22:47.2 m1   0.5747 21.842 1.610 V RR0
15       04:46:05.00 +31:22:52.9 m1   0.5085 20.918 0.323 V RR0
16       04:46:04.64 +31:22:42.0 m1   0.4902 19.179 0.330 V RR?
17       04:46:02.96 +31:23:09.2 m1 ----     19.0   0.9   V SR?
18       04:46:05.85 +31:23:03.3 m1   0.5102 18.876 0.768 V RR?
==========================================================================

Supplementary Notes 

Palomar 2 is a distant, heavily obscured globular cluster, close to the 
Galactic plane, in the direction of the Galactc anticentre.
Because of its location, the cluster is challenging to observe and early 
searches for variable stars were unsuccessful.

The first published search was by Rosino & Pinto (1973) who concluded 
that the cluster does not contain any red variables.  However, the 
possibility that any RR Lyrae may be present could not be ruled out.

Later, Harris et al. (1997) published a CM diagram that showed a
well populated red horizontal branch with a sparser extension to the 
blue. Based on this, they concluded that it is likely that Pal 2 
contains RR Lyrae variables, but their observational data were not 
suitable for performing a search.  Subsequently, a CM diagram published 
by Sarajedini et al. (2007) confirmed that the HB is bimodal in color.

Eventually, some of the cluster's elusive RR Lyrae variable stars were 
discovered by Arellano Ferro et al. (2023, hereafter AF23).  For their
search, they employed difference imaging software.  The RR Lyrae variables 
were among the faintest objects they could detect in their images so their 
discovery was a major achievement.

All of the data in the above table are from the AF23  paper, with a
minor exception.   They listed 6 decimal places for the RR Lyrae 
periods they derived, but only 4 decimal places are listed in the 
above table.  
=====================================================================
Discovery of the variable stars in Palomar 2:

V1-18
   AF23 with RA, dec (J2000) and an identifcation chart
   These are all considered to be cluster members.  

   They also discovered 7 variables which were not confirmed
   cluster members. They numbered these variables SV1-SV7.  
   In addition, they identified a few more variables in the Gaia-DR3
   data base.  None of these were considered to be cluster members.
======================================================================
References

Arellano Ferro, A., Bustos Ferro, I., Muneer, S., Giridhar, S. 2023,
Rev. Mex A&A, 59, 3 (AF23)

Harris, W. E., Durrell, P. R., Petitpas, G. R., Webb, T. M., Woodworth,
S. C. 1997, AJ, 114, 1043

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

Rosino, L. & Pinto, G. 1973, IAU Colloq. No. 21, Variable Stars in
Globular Clusters and in Related Systems, 21

Sarajedini, A., Bedin, L. R., Chaboyer, B., Dotter, A., Siegel, M.,
Anderson, J., Aparicio, A., KIng, I., Majewski, S., Marin-Franch, A.,
Piotto, G., Reid, I. N., Rosenberg, A. 2007, AJ, 133, 1658
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