176 V404 CYGNI (X-RAY NOVA) Range: 11.7-19.2V Position: 20 24 03.83 +33 52 02.9 (J2000, from .dat file) Magnitude: V=18.030 B-V=2.161 (in .dat file) ID RA (2000) DEC X Y N V ERR B-V ERR a) Comparison star sequence 1 20 24 18.1 +33 57 57 178 354 3 11.039 0.118 0.525 0.061 2 20 24 20.4 +33 56 26 207 263 3 11.260 0.103 0.307 0.051 3 20 24 28.3 +33 51 13 305 -50 3 12.289 0.016 0.522 0.012 4 20 23 56.5 +33 48 17 -92 -226 3 12.497 0.014 0.479 0.013 5 20 24 07.2 +33 50 52 42 -71 3 12.815 0.014 0.684 0.010 6 20 24 08.9 +33 54 38 63 155 3 13.164 0.012 0.715 0.013 7 20 23 53.4 +33 52 25 -130 22 3 13.361 0.015 1.106 0.008 8 20 24 29.9 +33 48 41 325 -202 3 13.757 0.014 0.662 0.012 9 20 23 52.8 +33 53 50 -137 107 3 14.125 0.017 0.618 0.013 10 20 24 18.7 +33 53 13 185 70 3 14.385 0.013 0.804 0.007 11 20 23 57.2 +33 56 39 -82 276 3 14.528 0.010 1.269 0.006 12 20 24 26.1 +33 49 52 278 -131 3 14.895 0.012 0.762 0.010 13 20 23 56.0 +33 53 29 -97 86 3 15.220 0.021 1.034 0.023 14 20 23 55.3 +33 51 15 -107 -48 3 15.599 0.016 0.920 0.007 15 20 24 04.3 +33 50 32 6 -91 3 16.141 0.016 0.921 0.009 16 20 24 04.7 +33 52 52 11 49 3 16.702 0.013 1.182 0.026 17 20 24 08.7 +33 52 13 61 10 3 17.552 0.051 1.414 0.028 18 20 24 03.6 +33 53 22 -2 79 3 18.285 0.034 1.336 0.187 b) Wide-colour extension for CCD calibration 20 24 14.2 +33 47 41 129 -262 3 12.727 0.013 0.374 0.012 20 23 52.2 +33 49 00 -145 -183 3 13.131 0.016 0.488 0.013 20 23 49.8 +33 54 48 -174 165 3 14.920 0.014 2.080 0.021 20 24 06.7 +33 52 55 36 52 3 15.953 0.013 2.507 0.046 20 23 49.1 +33 50 08 -183 -115 3 15.522 0.014 3.124 0.018 Notes: 1. Stars 1 and 2 are saturated, and their magnitudes and colours could have errors of +/- 0.2 magnitude. They should be used with care. 2. AAVSO chart 202033(f) dated June 1989 shows seven comparison stars, four of which are part of this sequence, two are highly coloured and are included as part of the CCD colour extension shown above, and one star on the AAVSO chart, 119, was not included in the new photometry. The six stars in common are: Henden AAVSO star V B-V v 4 12.497 0.479 127 blue 12.727 0.374 129 5 12.815 0.684 131 7 13.361 1.106 133 9 14.125 0.618 143 red 14.920 2.080 151 3. Udalski and Kaluzny, PASP,103,198,1991, present a detailed discussion of this variable, including the fact that V404 Cyg is the southern component of a magnitude 18 double star with a separation of 1.4 arcsec. The northern red component, which is a visual and not a physical companion, was measured by them as V=18.903 and B-V=1.717. V404 Cyg itself is slightly fainter than this at quiescence, approximately V=19.2. Udalski and Kaluzny also includes some photoelectrically determined comparison star magnitudes. Three of the stars are common to both sequences: Henden Udalski & Kaluzny star V B-V V B-V 5 12.815 0.684 12.817 0.706 C1 red 15.953 2.507 15.940 2.470 C2 16 16.702 1.182 16.715 1.162 C3 4. This nova has had visual outbursts in 1938, 1956, 1978 and 1988. Bruce Sumner 20 July 2000