COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 667 Konkoly Observatory Budapest 1972 April 27 PHOTOGRAPHIC B, V PHOTOMETRY OF Sco X-1 77 blue and 72 yellow, mostly simultaneous exposures were made with the 20-20 inch Yale-Columbia double astrograph at El Leoncito, San Juan, Argentina, of Sco X-1. The blue exposures, on Kodak 103 aO emulsion, were made without the usual filter normally used to eliminate undesirable ultraviolet from the Johnson B band. However, we may be sure that most of this light was absorbed by the four glass components of the Ross-objective lens system. The yellow observations, on Kodak 103 aD, were all made through a Schott GG14 filter. In addition to these south American observations, we obtained 71 blue exposures of Sco X-1 during the same period, with the Yale 40 inch Ritchey-Chretien reflector at Bethany, Connecticut, U.S.A. This series, on Kodak 103 aO emulsion, used a Schott GG13 filter to eliminate undesirable ultraviolet light from the Johnson B band. [FIGURE 1] Figure 1. Field of Sco X-1 with comparison stars. Figure 1 shows Sco X-1 and its surroundings. The two bright stars are BD -15deg4300 and -15deg4301. The stars 1, 2,...5 were measured by A. Sandage et. al. The stars A, a, b and c were used as comparison stars for the present photometry. The U, B, V photometry of these was done by Dr. R. McClure at our request, at the Interamerican Observatory at Tololo. Table 1 gives the U, B, V results as obtained by McClure and Sandage et. al. Sco X-1 and the comparison stars A, a, b and c were measured on all the available plates with the Yale iris photometer. In the reduction of the blue exposures we used the colour equation B'=B+0.05 (B-V) whereas the yellow exposures were reduced without a colour equation on V. For each exposure a separate reduction curve was used. The individual South American and North American results are given in Table 2 and Table 3 respectively. Altough the northern and southern observations cover approximately the same period, there is only one night (2439610) with data from both hemispheres. The two series agree within the observational error. The standard error of a single apparent magnitude as given in Tables 2 and 3 is +-0.06m. Only the South American observations from nights with more than 7 exposures have been represented graphically (Figures 2 and 3). [FIGURE 2-3] Figures 2 and 3. Brightness of Sco X-1 in both B and V. It is seen that the brightness varies considerably during a single night, whilst there is no evidence of periodicity. There is a marginal indication from all observations that the star is slightly bluer when bright. The mean colour index, using all the data, is found to be B-V=+0.20+0.01 in good accord with the photoelectric measures by Sandage et. al. We are indebted to Dr. R.D. McClure for his U, B, V photometry of the comparison stars. We thank Mr J. Stordy for the Bethany plates. We gratefully acknowledge the assistance from Mrs. K. DeVorkin with the measurements and the reduction. The work was partly supported by a grant from the NSF. A.J. WESSELINK and C. CESCO Yale University Observatory Reference: A. Sandage et. al., Ap.J. 146, 316 (1966). [BIBCODE 1966ApJ...146..316S ] Table 1 Star V B-V U-B -15d 4300 8.5 +0.25 +0.22 15 4301 9.88 +0.33 +0.27 1 14.97 +0.94 +0.41 2 16.25 +1.05 +0.43 3 14.17 +1.16 +0.87 4 14.47 +0.84 +0.33 5 14.46 +0.83 +0.26 A 11.34 +0.69 +0.15 a 11.49 +1.32 +1.23 b 12.37 +0.84 +0.35 c 13.36 +0.77 +0.24 Table 2 El Leoncito, San Juan, Argentina J.D. hel. 2430000+ B V 9522.846 13.16 - 9527.865 13.28 - 9533.867 12.63 - 9537.864 13.42 - 9538.868 12.49 - 9555.827 12.72 - 9556.859 12.60 - 9557.842 13.16 - 9567.794 12.89 - 9586.662 12.83 12.68 85.676 12.73 12.41 86.690 12.64 12.51 86.704 13.00 12.61 86.717 13.18 12.80 86.731 12.91 12.52 86.745 12.91 12.75 86.759 12.81 12.51 86.773 12.67 12.49 86.787 12.76 12.54 86.800 12.68 12.42 86.814 12.62 12.40 86.829 12.68 12.50 86.842 12.74 12.45 86.856 12.58 12.48 86.870 12.63 12.39 86.884 13.03 12.55 86.904 12.72 12.89 9590.679 13.27 12.94 90.693 13.29 13.21 90.707 12.99 12.76 90.720 13.09 12.79 90.738 13.03 12.89 90.752 12.90 12.59 90.766 12.73 12.45 90.779 12.60 12.49 90.797 12.68 12.40 90.804 12.59 12.40 90.824 12.59 12.49 9590.838 12.68 12.27 90.856 12.78 12.32 90.869 12.79 12.70 90.883 12.73 12.36 90.897 12.78 12.55 90.911 12.60 12.44 9591.829 12.32 - 91.843 12.32 - 91.856 12.30 - 91.870 12.28 - 91.884 12.40 - 9610.712 12.44 12.26 10.726 12.38 12.21 10.740 12.56 12.19 10.754 12.49 12.26 10.771 12.36 12.28 10.785 12.35 12.28 10.799 12.47 12.38 10.812 12.49 12.33 9616.864 12.76 - 16.880 12.81 - 16.897 12.59 - 16.914 12.65 - 9617.856 12.93 12.70 17.873 13.02 12.76 17.891 12.91 12.76 17.908 13.08 12.89 9620.869 - 12.42 20.882 - 12.37 20.896 - 12.28 20.910 - 12.27 9622.694 12.52 12.38 22.707 12.52 12.30 22.721 12.56 12.31 22.735 12.56 12.31 22.752 12.59 12.43 22.766 12.59 12.45 22.780 12.38 12.31 22.794 12.56 12.45 22.811 12.52 12.39 22.825 12.69 12.41 22.839 12.52 12.35 22.853 12.62 12.47 Table 3 Bethany, Connecticut, U.S.A. J.D. hel. 2430000+ B 9584.891 12.64 9589.849 13.53 9592.850 12.45 9593.813 13.06 9609.772 12.27 09.791 12.23 9610.804 12.41 10.814 12.47 10.823 12.53 10.831 12.62 9611.829 12.63 11.840 12.63 11.848 12.44 11.857 12.59 11.865 12.57 9614.764 12.31 14.770 12.44 14.775 12.48 14.780 12.41 14.820 12.35 14.826 12.40 14.830 12.38 14.835 12.59 9624.762 12.72 24.773 12.70 24.782 12.76 24.788 12.72 9627.801 12.67 27.808 12.68 27.814 12.70 27.820 12.77 9628.750 12.73 28.755 12.89 28.761 12.70 28.767 12.77 9641.750 13.24 41.755 13.23 41.761 13.46: 41.766 13.08 9642.726 13.02 42.732 13.11 42.737 13.09 42.743 13.12 9844.711 12.34 44.717 12.34 44.722 12.34 44.728 12.31 44.734 12.45 9645.727 13.27 45.732 13.23 45.737 13.23 45.743 13.23 45.761 13.18 9648.674 12.98 48.680 12.99 48.686 12.94 9698.624 12.69 9910.910 13.02 10.924 13.04 10.929 13.07 9913.926 12.53 13.932 12.62 9945.892 12.56 45.898 12.53 45.902 12.53 9948.892 12.77 48.898 12.85 9966.860 12.57 10013.712 12.54 13.718 12.55 13.722 12.52