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(vsnet 934, Brian Skiff)
Below are positions, identifications, and multicolor photometric data for stars in two comparison sequences around the dwarf nova CM Delphini. One sequence was published be Andronov et al. in 1993 (IBVS 3932), and the other appears in the Misselt 1996 paper (PASP 108, 146). Andronov et al. used just three stars from two different sources as calibration standards, and they admit rather large errors for the data (+/- 0.07 in V, for example). These large errors probably mask any systematic differences with the Cousins system for the VRI colors. Misselt used larger numbers of Landolt equatorial standards as calibration, and his quoted uncertainties appear to be realistic, if also larger than one might like.
There are two stars in common, and the comparison is not flattering. Both sets of data are listed for the two stars in the first table below. For the brighter star, the figures agree (barely) to within the stated errors; for the fainter star, the magnitudes and colors are clearly discordant, and one can suspect the Andronov data are more likely to be at fault, since they note problems when comparing results for other stars in the same IBVS note.
\Brian Skiff (bas@lowell.edu)
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CM Del 20 24 57.0 +17 17 55 (McNaught 1986, IBVS 2926)
Andronov stars RA (2000) Dec s V U-B B-V V-R R-I
GSC 1636-0710 20 24 56.6 +17 14 52 U 12.63 0.36 0.74 0.57 0.45
GSC 1636-0300 20 24 59.2 +17 14 38 U 12.96 1.16 1.18 0.86 0.68
Andronov 3 20 24 57.3 +17 19 48 U 13.60 0.24 0.38 0.25 0.22
13.71 0.40 0.21 (Misselt 4)
Andronov 4 20 25 05.6 +17 15 45 U 14.54 0.15 0.23 0.23 0.24
14.70 0.84 0.49 (Misselt 14)
Andronov 5 20 25 05.5 +17 16 04 U 13.27 0.14 0.65 0.50 0.39
GSC 1636-1458 20 25 11.3 +17 16 42 U 11.97 0.17 0.55 0.47 0.35
Misselt stars RA (2000) Dec s V B-V V-R
[M96a] CM Del star 2 20 24 55.0 +17 17 22 U 14.392 1.054 0.591
.041 .051 .053
[M96a] CM Del star 4 20 24 57.3 +17 19 48 U 13.706 0.404 0.212
.042 .051 .054
[M96a] CM Del star 5 20 24 58.0 +17 16 35 S 15.516 1.150 0.581
.047 .059 .059
[M96a] CM Del star 6 20 24 58.3 +17 16 32 U 14.743 0.710 0.412
.043 .052 .055
[M96a] CM Del star 7 20 24 58.3 +17 17 55 A 16.328 0.959 0.557
.043 .056 .055
[M96a] CM Del star 10 20 24 59.9 +17 17 07 U 15.045 0.778 0.425
.041 .051 .054
[M96a] CM Del star 11 20 25 00.1 +17 16 50 U 15.213 0.684 0.355
.043 .052 .055
[M96a] CM Del star 12 20 25 01.3 +17 17 33 U 12.616 0.723 0.398
.041 .050 .053
[M96a] CM Del star 14 20 25 05.6 +17 15 45 U 14.699 0.835 0.490
.041 .051 .053
star 6 = GSC 1636-1206.
star 12 = GSC 1636-1104.
