NGC 6638 / C1827-255
RA: 18:30:56.10 DEC: -25:29:50.9 (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
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ID Position Mem Period <mag> ampl C Type Notes/
RA Dec Flag Remarks
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1 18:30:01.77 -25:16:29.1 u ---- 15.42 0.63 P ?
2 18:30:02.58 -25:37:25.0 u ---- 13.22 0.39 P CST?
3 18:30:20.19 -25:37:51.4 u 260.0 15.33 3.65 P M
4 18:30:21.75 -25:25:39.1 u ---- 15.76 0.68 P ?
5 18:30:31.33 -24:14:08.6 u ---- 15.18 0.49 P CST?
6 18:30:32.12 -25:25:46.8 u ---- 15.86 0.40 P CST?
7 18:30:35.42 -25:28:10.7 u ---- 16.59 0.57 P CST?
8 18:30:37.42 -25:36:29.6 u ---- 16.48 1.19 P ?
9 18:30:44.80 -25:29:05.1 u ---- 15.95 0.50 P CST?
10 18:30:54.36 -25:30:54.0 m1 ---- 15.92 0.44 P CST?
11 18:30:54.86 -25:32:20.4 u ---- 16.51 1.15 P ?
12 18:31:10.61 -25:36:27.2 u 279.0 14.65 3.01 P M
13 18:31:14.07 -25:16:16.6 u 209.0 14.58 4.36 P M
14 18:31:20.82 -25:14:58.3 u ---- 15.60 0.40 P CST?
15 18:31:37.23 -25:18:09.9 u 156.0 15.18 3.65 P M
16 18:31:45.63 -25:20:40.3 u ---- 15.21 0.75 P ?
17 18:31:50.15 -25:18:00.8 u ---- 16.39 1.22 P ?
18 18:31:50.73 -25:26:07.2 u ---- 14.33 0.50 P CST?
19 18:31:53.77 -25:12:29.3 u ---- 15.26 0.88 P ?
20 18:30:53.00 -25:30:12.1 m1 0.3145 15.97 0.57 P RR1
21 18:30:53.68 -25:29:45.0 f 0.3290 16.17 0.40 P RR1
22 18:30:53.91 -25:29:42.9 f 0.3500 15.80 0.56 P RR1
23 18:30:54.18 -25:29:29.1 m2 0.3255 15.94 0.56 P RR1
24 18:30:54.58 -25:29:27.9 m1 0.6655 16.06 0.71 P RR0
25 18:30:55.56 -25:30:04.1 f 0.6728 15.79 0.66 I RR0 Sk
26 18:30:55.64 -25:30:08.8 m1 0.6674 15.85 0.47 I RR0 Sk
27 18:30:55.91 -25:30:09.3 m1 0.5997 15.87 0.68 I RR0 Sk
28 18:30:56.03 -25:29:12.2 f 0.3150 15.90 0.51 P RR1
29 18:30:56.11 -25:29:53.9 f 0.2579 15.92 0.31 I RR1 Sk
30 18:30:56.47 -25:30:07.6 m1 0.5065 16.00 0.75 I RR0 Sk
31 18:30:56.64 -25:29:59.5 f 0.4580 15.88 0.67 I RR0 Sk
32 18:30:56.57 -25:29:49.8 f 0.5683 15.65 0.35 I RR0 Sk
33 18:30:56.91 -25:30:10.8 m1 0.3238 16.07 0.22 I RR1 Sk
34 18:30:57.37 -25:29:51.1 m1 ---- -- -- ?
35 18:30:57.77 -25:30:05.8 f ---- -- -- ?
36 18:30:57.98 -25:30:08.3 m1 ---- -- -- ?
37 18:30:50.43 -25:29:21.3 m1 0.2790 16.29 0.54 P RR1 Note
38 18:30:52.13 -25:28:31.3 f 0.3080 16.14 0.36 P RR1 Note
39 18:30:54.24 -25:29:00.8 f 0.2575 15.91 0.57 P RR1
40 18:30:55.09 -25:32:16.5 u 0.2990 16.71 0.54 P RR1 Note
41 18:30:59.14 -25:30:26.2 f 0.2975 16.22 0.70 P RR1
42 18:30:59.49 -25:27:57.7 u 0.3450 16.30 0.48 P RR1 Note
43 18:31:00.41 -25:30:58.9 m1 0.2980 16.35 0.53 P RR1 Note
44 18:31:01.1 -25:30:28 m1 0.2655 16.32 0.68 P RR1
45 18:31:02.07 -25:30:39.0 m1 0.2955 16.32 0.50 P RR1 Note
46 18:29:58.65 -25:26:08.8 u ---- 16.29 1.07 P
47 18:30:00.51 -25:21:08.2 u ---- 16.23 0.74 P
48 18:30:00.33 -25:22:34.3 u ---- 13.45 1.14 P
49 18:30:06.35 -25:42:32.2 u ---- 14.05 1.02 P
50 18:30:21.60 -25:19:26.7 u ---- 15.97 0.80 P
51 18:30:21.67 -25:35:07.9 u ---- 16.23 1.01 P
52 18:30:30.55 -25:35:34.8 u ---- 16.03 1.25 P
53 18:30:44.00 -25:30:32.7 u ---- 15.70 0.61 P
54 18:31:05.61 -25:11:37.2 u ---- 14.79 1.75 P
55 18:31:04.41 -25:17:07.6 u ---- 15.65 0.57 P
56 18:31:17.70 -25:21:43.7 u ---- 14.82 1.00 P
57 18:31:16.78 -25:42:29.9 u 380.0 16.44 1.73 P M?
58 18:31:31.36 -25:18:10.8 u ---- 16.17 0.96 P
59 18:31:33.25 -25:13:17.7 u ---- 15.19 1.67 P
60 18:31:41.31 -25:20:08.3 u ---- 16.35 1.31 P
61 18:31:51.37 -25:12:48.6 u ---- 15.58 1.70 P
62 18:31:47.43 -25:35:34.4 u ---- 16.03 1.25 P
63 18:31:49.49 -25:39:36.5 u 213.0 15.36 3.28 P M
64 18:30:56.32 -25:30:03.7 f 0.2483 16.14 0.20 I RR1
65 18:30:55.59 -25:29:43.6 f 0.3682 15.85 0.28 I RR1
66 18:30:55.02 -25:29:47.1 f 0.6402 15.78 0.24 I RR0
67 18:30:56.84 -25:29:46.8 f 0.6414 15.67 0.13 I RR0
68 18:30:56.24 -25:30:04.4 f 0.8329 15.97 0.87 I RR0
69 18:30:54.83 -25:30:01.5 m1 38.8 12.30 0.22 I SR
70 18:30:55.82 -25:30:01.0 f 80.2 11.77 0.45 I SR
71 18:30:56.01 -25:29:57.3 f 11.92 0.10 I L
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Supplementary Notes
The data in the above table are from the following sources.
V1-63:
The RA and dec in the above table are from Samus et al. (2009)
unless indicated "Sk" in the remarks column in which case they
are from Skottfelt et al. (2015).
Samus et al. pointed out that there were serious errors in the
RA and dec values published earlier by Rutily & Terzan (1977).
The periods, magnitudes and classifications are based mainly on
the data of Rutily & Terzan (1977). They treated the variable
stars in two groups: red variables (V1-V19 and V46-V63) and
blue variables (V20-V45).
Most of the red variables are located outside the tidal radius
(~4.7 arcminutes according to the 2010 update of the 1996 Harris
catalogue) and probably belong to the field around the cluster.
Consequently they are all listed in the Moscow GCVS or NSV
catalogues. Samus et al. (2009) listed the GCVS and/or NSV
designations for these variables in Table 1 of their paper.
Skottfelt et al. (2015) published RA, dec, periods, magnitudes
and amplitudes for some of the blue variables. These stars
are indicated "Sk" in the remarks column.
V64-71:
All the data are from the discovery paper by Skottfelt et al.
(2015).
A BV CM diagram by Piotto et al. (2002) based on HST data shows a blue
straggler sequence and a horizontal branch that is populated on both
sides of the instability strip.
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Notes on individual stars:
V37, V38, V40, V42, V43, V45:
Smith & Stryker (1986) obtained low-resolution spectra for these
RR Lyrae variables. Based on the radial velocities they derived,
they concluded that V37, V38, V42, V45 were probable members and
that the membership membership status of V40 and V43 was
questionable.
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Discovery of the variable stars in NGC 6638:
V1-19
Terzan (1968) with an ID chart
Three of these variables #9, #10 and #11 were listed as V1-3
by Sawyer Hogg (1973) in her 3rd catalogue. The remaining 16
were not included because she considered them to be field stars.
No elements were listed by Sawyer Hogg (1973) for any of the
variables.
Terzan's original numbering system (V1-19) has been used in the
above table because it was adopted in a later paper by Rutily & Terzan
(1977) for the variable stars in and around NGC 6638. The 1977 paper
includes ID charts for all of the variables.
V20-45 = V4-29 of Sawyer Hogg et al. (1974) and Terzan & Rutily (1975)
The x,y coordinates were listed in both of the above papers.
The numbers V20-45 were assigned in a later paper by Rutily &
Terzan (1977). In their 1977 paper, Rutily & Terzan published
an ID chart for V20-45.
V46-63
Rutily & Terzan (1977) with 1950 RA and Dec and an ID
chart for V1-19 and V44-63.
V64-71
Skottfelt et al. (2015) with RA, dec and a finding chart
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References
Harris, W. E. 1996, AJ, 112, 1487
Piotto, G., King, I. R., Djorgovski, S. G., Sosin, C., Zoccali, M.,
Saviane, I., De Angeli, F. and 5 coauthors, 2002, A&A, 391, 945
Prudil Z., Arellano Ferro, A. 2024, MNRAS, 534, 3654
Rutily, B. & Terzan, A. 1977, A&AS, 30, 315
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
Sawyer Hogg, H., Terzan, A., Rutily, B. 1974, Comptes Rendus, 279, 333
Smith, H. A. & Stryker, L. L. 1986, PASP, 98, 453
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
Terzan, A. 1968, Pub. Obs. Haute Prov., 9, No. 24
Terzan, A. & Rutily, B. 1975, A&A, 38, 307
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