COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2678 Konkoly Observatory Budapest 4 March 1985 HU ISSN 0374 - 0676 PHOTOELECTRIC PHOTOMETRY OF EPSILON AURIGAE Epsilon Aurigae was observed during the period 1982-1985 at the Jagiellonian University Observatory in Cracow (Fort Skala) and at the Station in the Bieszczady Mountains (lambda=-1h29m, phi =49d10'). These observations were made in coordination with the observational campaign of the star (Genet, Stencel 1982) Two instruments in Cracow: the 500 mm Cassegrain reflector (hereafter denoted as R) and the 350 mm Maksutov reflector (denoted as M) as well as the 203 mm refractor (denoted as A) at the Mountain Station, equipped with one- channel photometers with UBV filters and photomultipliers: an EMI 9789 QB at the R-telescope and a Russian made FEU 92 at the others, were used in the presented observations. All these systems are close to the standard UBV system. The diaphragms used were: 24, 40 and 122 arcsec, respectively. The differential photometry of e Aurigae in respect to Lambda Aurigae as comparison star were performed during 102 nights. The accepted magnitudes of the comparison star: U=5.456m, B=5.332m, V=4.710m are mean values of measurements from the Photometric Catalogue (Blanco et al. 1968). We attempted to make several measurements in each observational season, their actual number is given in column denoted N. However, for a number of reasons, it was not always possible. Due to this, our data are of unequal quality, so we decided to present them in different tables. When a number of individual measurements in B or V is greater than 5, observations are given in Table I, whereas for N<6 they are given in Table II. There are but a few observations in U-band, so they are listed in the separate Table III. Each measurement has been corrected for atmospheric extinction and the measurement means, reduced to the UBV system, are given in the respective column of each Table. The moments of observations, expressed in heliocentric MJD, are means of individual moments of measurements. The transformation formulae from instrumental ubv system to the UBV system are: U_lambda - U_epsilon = u_lambda - u_epsilon + a_u ((U-B)_lambda - (U-B)_epsilon) B_lambda - B_epsilon = b_lambda - b_epsilon + a_b ((B-V)_lambda - (B-V)_epsilon) V_lambda - V_epsilon = v_lambda - v_epsilon + a_v ((B-V)_lambda - (B-V)_epsilon) where the values of coefficients are : instrument a_u a_b a_v ----------------------------------------------------------- R +.0017 +-.0187 -.2846 +-.0100 -.1034 +-.0012 M +.030 +-.012 -.146 +-.008 A +.0143 +-.0025 -.1252 +-.0030 ----------------------------------------------------------- Atmospheric extinction was determined for each night. Sometimes, particularly when the differences of air masses for both stars were small throughout the observational season the mean coefficients were accepted (C =0.4m and C =0.55m for Cracow, C_V=0.2m and C_B=0.35m for the Mountain Station). In such cases in the column denoted ext we give admissible error in photometry, assuming fifty percent change in the accepted values of the extinction coefficient. In all cases this error did not exceed 0.005m. Measurements were recorded on paper tapes and due to small dynamics of the receiver its different ranges had to be used. These differences were determined for each night and the determination errors are also introduced into values presented in the column denoted SD. This does not apply to the R-telescope observations after MJD 45671.0, in which a digital receiver was used. The column denoted SD gives the standard deviation of measurements, together with mentioned above determination error, however it is meaningful only when the number of observations is sufficiently large. The observed B and V light curves, along with colour index B-V, are presented in Figure 1. It can be seen from the light curves that in addition to the eclipsing variability epsilon Aurigae shows additional brightness changes. They are especially well discernible during totality. These changes are well above measurement errors and they have been reported also by other authors (see Hopkins and Stencel 1983). Their analysis will be published later. We have not been lucky enough to record supected flare activity of the star (Nha and Lee 1983 ). Our observations confirm the anomaly reported by Osi et al. (1984) and Boyd et al. (1984) near the third contact predicted by Gyldenkerne (1970). In both colours the rapid increase of brightness and its subsequent decrease can be observed. Moreover, near the fourth contact after the maximum we observed brightness decrease in both colours, as well as changes of B-V colour index. As can be seen from Figure 1 the colour changes are very small. It seems that mean values of B-V index calculated separately for different phases are somewhat different, but these differences are small, slightly greater than 1sigma level of significance. These means are denoted in Figure 1 by crosses. The determination of time of contacts from our observations is difficult. Nevertheless, it seems that the second contact occurred a little earlier than predicted, whereas the third and the fourth contacts later than predicted. Timing of minimum is difficult too, because light curve is asymmetric. Table I : B, V photometry of Epsilon Aurigae ----------------------------------------------------------------------------------------------------------- Date MJD B SD N ext MJD V SD N ext inst observer ----------------------------------------------------------------------------------------------------------- Apr5/6 1982 45064.821d 3.506m+-.005m 9 - 45064d804 2.989m +-.004m 9 - R MW Jul 29/30 180.067 3.706 .009 9 - 180.044 3.126 .005 11 - R MW Oct 2/3 245.010 4.013 .016 6 - 245.040 3.473 .008 6 - M SZ Oct 5/6 248.001 4.069 .012 7 .002 24s.001 3.518 .006 6 .001 M SZ Oct 22/23 265.096 4.096 .003 11 - 265.071 3.547 .002 11 - A MW Oct 22/23 265.095 4.081 .016 7 - 265.094 3.501 .006 7 - M SZ Oct 29/30 272.091 4.105 .004 13 .002 272.051 3.572 .004 15 - R MW Nov 6/7 280.062 4.159 .003 11 - 280.042 3.634 .002 11 - R MW Nov 7/8 281.062 4,167 .006 10 - 281.041 3.642 .002 10 - R MW Nov 11/12 285.054 4.188 .003 12 - 285.032 3.646 .003 11 - R MW Nov 21/22 294.992 4.231 .020 10 - 294.992 3.696 .017 7 - M SZ Nov 27/28 301.007 4.282 .003 10 1 300.990 3.737 .002 10 - R MW Jan 12/13 83 346.870 4.289 .007 9 .001 346.869 3.728 .005 9 .001 M SZ Feb 24/25 389.845 4.349 .009 10 .002 389.846 3.794 .006 9 .002 M SZ Feb 25/26 390.875 4.364 .004 10 - 390.901 3.780 .004 11 - M MW Mar 12/13 405.865 4.355 .005 10 - 405.842 3.798 .002 12 - A MW Mar 13/14 406.771 4.351 .006 10 - 406.744 3.800 .006 9 - A MW Mar 13/14 406.745 4.348 .008 8 .001 406.796 3.807 .009 9 .001 M SZ Apr 17/18 441.819 4.263 .005 12 - 441.790 3.708 .005 12 - M MW Aug 19/20 566.024 4.329 .017 7 - 566.003 3.660 .012 7 - M SZ Aug 22/23 569.000 4.214 .010 8 - M SZ Aug 26/27 573.050 4.258 .012 8 - M SZ Aug 30/31 577.003 4.292 .012 9 - 576.972 3.779 .004 9 - M SZ Sep 2/3 579.972 4.306 .008 6 - 579.972 3.731 .030 6 - M SZ Sep 8/9 585.986 4.312 .022 7 - 585.987 3.792 .007 9 - M SZ Sep 15/16 593.015 4.377 .005 16 - 593.019 3.795 .005 16 - M SZ Sep 27/28 604.956 4.342 .004 12 - 604.957 3.766 .004 11 - M SZ Sep 29/30 607.111 4.327 .010 9 .002 607.112 3.768 .006 9 .001 M SZ Oct1/2 1983 609.092 4.344 .005 19 .002 609.091 3.767 .004 19 .001 M SZ Oct 1/2 609.144 4.305 .004 12 - 609.120 3.769 .003 13 - R MW Oct 5/6 613,129 4.324 .009 6 .001 613.128 3.740 .009 6 .001 M SZ Oct 18/19 626.154 4.331 .004 11 .001 626.125 3.758 .004 11 .001 M SZ Oct 27/28 635.068 4.315 .006 16 .001 635.068 3.754 .006 16 .001 M SZ Oct 27/28 635.107 4.287 .004 11 - 635.084 3.731 .003 11 - R MW Nov 8/9 45647.086 4.296 .005 13 .001 45647.045 3.713 .003 12 .001 A MW Nov 9/10 648.040 4.302 .006 10 .001 648.040 3.719 .004 10 .001 M SZ Nov 11/12 650.052 4.302 .006 13 .001 650.052 3.708 .007 13 .001 M SZ Dec 2/3 670.977 4.338 .006 30 .001 670.978 3.714 .006 30 .001 M SZ Dec 3/4 672.033 4.330 .024 12 .001 671.986 3.757 .003 14 .001 R MW Dec 4/5 672.937 4.324 .006 13 .001 672.936 3.765 .006 13 .001 M SZ Dec 4/5 672.966 3.718 .022 6 .002 R MW Dec 5/6 673.998 4.370 .005 20 .001 674.035 3.748 .005 20 .001 M SZ Dec 11/12 679.992 4.344 .003 10 .001 679.966 3.753 .003 10 .001 A MW Dec 12/13 681.051 4.334 .006 18 .001 681.052 3.747 .007 18 .001 M SZ Dec 14/15 682.921 4.312 .008 8 .001 682.908 3.747 .008 8 .001 M SZ Dec 14/15 682.976 4.352 .002 10 - 682.950 3.759 .002 10 - A MW Dec 15/16 683.980 4.339 .003 10 - 683.947 3.748 .001 10 .001 A MW Dec 29/30 697.895 4.323 .007 19 .001 697.895 3.749 .005 19 .001 M SZ Dec 29/30 697.962 4.294 .002 13 .001 697.920 3.746 .002 19 .001 R MW Jan 11/12 84 710.861 4.251 .005 15 .001 710.861 3,691 .006 15 .001 M SZ Jan 11/12 710.922 4.216 .006 12 .001 710.864 3.703 .002 13 .002 R MW Jan 12/13 711,883 4.265 .005 12 .001 711.882 3.701 .006 12 .001 M SZ Jan 12/13 711.882 3.699 .002 12 .001 R MW Jan 16/17 715.942 4.256 .006 8 .001 715.946 3.711 .008 8 .001 M SZ Jan 23/24 722.894 4.271 .009 7 .001 722.895 3.719 .007 7 .001 M SZ Feb 18/19 748.767 3.664 .003 16 .001 R MW Feb 29/Mar 1 759.755 4.227 .010 6 .001 759.756 3.599 .009 6 .001 M SZ Feb 29/Mar 1 759.793 4.190 .005 7 .001 759.756 3.603 .002 14 .001 R MW Mar 1/2 760.806 4.184 .003 15 - 760.772 3.592 .004 14 .001 R MW Mar 14/15 773.760 3.473 .001 6 .001 R MW Mar 19/20 778.862 3.985 -002 11 - 778.781 3.407 .004 14 - R MW Mar 19/20 84 778.827 3.981 .009 16 - 778.827 3.393 .006 16 - M SZ Mar 24/25 783.790 3.955 .008 7 - 783.791 3.339 .007 8 - M SZ Mar 27/28 786.842 3.885 .010 7 - M SZ Apr 3/4 793.832 3.832 .012 8 - 793.833 3.248 .012 8 - M SZ Apr 14/15 804.802 3.175 .014 6 - M SZ Apr 15/16 805.793 3.751 .008 6 - 805.806 3.202 .010 6 - M SZ Apr 25/26 815.797 3.703 .010 7 - 815.818 3.131 .009 6 - M SZ Jul 31/Aug 1 913.075 3.036 .004 10 - R MW Aug 14/15 45927.060 3.026 .009 8 - 45927.060 3.124 .011 8 - M SZ Aug 19/20 932.019 3.583 .008 8 - 932.018 3.057 .006 8 - M SZ Aug 22/23 935.025 3.603 .007 6 - M SZ Aug 24/25 937.091 3.058 .006 11 - A MW Sep 13/14 957.076 3.660 .004 8 - 957.022 3.062 .002 8 - A SZ Sep 24/25 967.991 3.638 .006 8 - 967.988 3.062 .005 10 - M SZ Sep 30/Oct 1 974.067 3.631 .006 6 - 974.067 3.058 .005 6 - M SZ Oct 18/19 991.999 3.518 .010 7 - 991.999 2.985 .009 7 - M SZ Oct 18/19 992.098 3.000 .004 14 .002 R MW Oct 19/20 993.084 3.506 .002 12 .003 993.093 2.996 .001 12 .002 R MW Oct 30/31 46004.082 3.542 .004 12 - 46004.049 3.007 .006 12 - A MW Nov 4/5 009.033 3.523 .007 7 M SZ Nov 4/5 009.070 3.518 .004 12 - 009.090 3.010 .006 12 - R MW Nov 7/8 012.067 3.519 .004 12 - 012.047 3.009 .001 11 - R MW Nov 12/13 017.032 3.021 .011 14 - R MW Nov 14/15 019.037 3.034 .007 12 .001 R MW Nov 30/Dec 1 034.997 3.548 .006 13 .001 034.973 3.026 .003 12 .002 R MW Dec 2/3 036.977 3.527 .003 11 .002 037.004 3.003 .003 10 .001 R MW Jan 15/16 85 080.919 3.654 .004 11 - 080.887 3.083 .005 11 - A MW Jan 16/17 081.856 3.661 .002 11 .001 081.832 3.084 .002 11 .001 A MW Jan 28/29 093.985 3.560 .007 7 - 093.941 3.036 .006 8 - M SZ Sep 11/12 82 45223.994 3.709 .038 3 .002 45223.995 3.148 .021 3 .002 M SZ Sep 12/13 225.011 3.876 .010 5 - 225.011 3.377 .016 5 M SZ Sep 15/16 228.012 3.842 .030 3 - 228.011 3.364 .011 3 - M SZ Sep 17/18 230.053 3.843 .030 4 .002 230.064 3.347 .009 2 .001 M SZ Sep 29/30 241.995 4.005 .008 5 - 241.997 3.443 .007 5 - M SZ Oct 21/22 263.997 4.005 .040 2 - 263.998 3.570 .016 2 - M SZ Oct 27/28 270.036 3.538 .020 2 .004 R MW Oct 27/28 270.055 4.221 .045 2 .001 270.054 3.625 .007 2 .001 M SZ Mar 23/24 83 416.803 4.288 . 1 .002 416.802 3.755 - 1 .001 M SZ Aug 22/23 568.999 3.667 .014 5 - M SZ Aug 26/27 573.093 3.710 .009 2 - M SZ Oct 13/14 621.084 4.324 .011 5 .001 621.083 3.761 .008 5 .001 SZ Oct 24/25 632.049 4.300 .012 3 .001 632.048 3.704 .012 2 .001 M SZ Dec 3/4 671.898 4.324 .015 3 .001 671.898 3.743 .014 3 .001 M SZ Jan 2/3 1984 701.924 4.300 .010 5 .001 701.924 3.725 .009 5 .001 M SZ Jan 8/9 707.942 4.267 .005 5 .001 707.943 3.707 .009 5 .001 M SZ Jan 12/13 711.899 4.235 .006 4 .001 R MW Feb 7/8 737.825 4.303 - 1 .001 737.833 3.715 .010 3 .001 M SZ Feb 13/14 743.754 4.293 .009 5 .001 743.754 3.698 .009 5 .001 M SZ Mar 1/2 760.874 4.139 .421 2 .002 760.874 3.498 .008 5 .002 M SZ Mar 14/15 773.820 4.132 - 1 - 773.816 3.452 .010 4 M SZ Mar 20/21 779.776 3.408 .021 4 .001 R MW Mar 21/22 780.768 3.386 .007 4 .005 R MW Mar 21/22 780.774 3.426 .048 2 .001 M SZ Mar 27/28 786.847 3.308 .012 4 - M SZ Apr 14/15 804.808 3.743 .008 5 - M SZ Jul 11/12 893.035 2.907 .017 2 - M SZ Jul 31/Aug 1 913.018 3.475 .038 5 - 913.018 2.866 .037 4 - M SZ Aug 27/28 84 45940.044 3.571 .012 5 - 5940.044 3.036 .006 5 - M SZ Sep 2/3 945.917 3.596 .040 3 - 945.918 3.004 .030 2 - M SZ Oct 1/2 975.014 3.671 .016 2 .003 975.014 3.140 .006 2 .002 M SZ Hoe 20/21 993.943 3.519 .008 2 - 993.946 2.979 .011 2 - M SZ Nov 4/5 46009.033 2.992 .006 5 - M SZ Nov 14/15 46019.053 3.519 .005 3 - R Aug 3/4 916.068 3.530 .038 5 - 916.062 3.037 .018 5 - M SZ Aug 9/10 922.020 3.584 .007 4 - 922.020 3.113 .016 4 - M SZ Aug 13/14 926.070 3.569 .006 4 - 926.071 3.045 .016 4 - M SZ Aug 22/23 935.025 3.055 .013 5 - M SZ Aug 23/24 936.022 3.622 .012 5 - 936.023 3.053 .011 5 - M SZ Table III : U photometry of Epsilon Aurigae Date MJD U SD N inst observer -------------------------------------------------------- Apr 5/61982 45064d837 3.890m +-.005 8 R MW Jul 29/30 180.078 4.128 .014 3 R MW Nov 6/7 280.082 4.616 .003 11 R MW Nov 7/8 281.082 4.629 .003 10 R MW -------------------------------------------------------- [FIGURE 1] Figure 1: B and V light curve of Epsilon Aurigae and B-V changes Taking into account ingress and egress observations only, the classic tracing-paper method yields: minimum MJD hel. = 455110d +-5d, fitting of Gaussian plus quadratic term gives: minimum MJD hel = 45512.2d +- 0.1d and fitting of straight lines (Gyldenkerne 1970) gives MJD hel = 45511.0d as division value of the second-third contact segment in half. We thank R.M. Genet, J.L. Hopkins and R.E. Stencel, the editors of Epsilon Aurigae Campaign Newsletter for sending us their publication. P. FLIN, M. WINIARSKI and S. ZOLA Jagiellonian University Observatory ul. Orla 171, 30-244 Krakow, Poland References : Blanco, V.M., Demers, S., Douglass, G.G., Fitzgerald, M.P., 1968, Photometric Catalogue, Publ.Naval Obs., Sec.Serie, vol. XXI. [BIBCODE 1968PUSNO..21....1B ] Boyd, L.J., Genet, R.M., Hall, D.S., 1984, I.B.V.S. No. 2562 Genet, R.M., Stencel, R.E., 1982, Campaign Newsletter No. 1 Gyldenkerne, K., 1970, Vistas in Astronomy 12, p. 199 [BIBCODE 1970VA.....12..199G ] Hopkins, J.L., Stencel, R.E., 1983, Campaign Newsletter No. 9 Oki, T., Sekiya, I., Hirayama, K., 1984, I.B.V.S. No. 2496 Nha, I.-S., Lee, S.J., 1983, I.B.V.S. No. 2405