COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3593 Konkoly Observatory Budapest 22 April 1991 HU ISSN 0374 - 0676 Epochs of Minimum Light For Eight Eclipsing Binary Star Systems An Optec SSP-3 photometer was used on the 41cm David Irons telescope at the observatory of the Charlotte Amateur Astronomers Club to make differential measurements of eight eclipsing binaries. Because of the sensitivity of the detector and the faintness and color of the stars, generally only V observations were attempted. The exception is R Canis Majoris, for which both B and V observations were made. The Hertzsprung method was used to find epochs of minimum light, which are presented in Table I. The epoch of R Canis Majoris is an average of the determinations from the observations in each filter. The residual for AA Andromedae was computed based on the light elements of Pierce (1951). Because the residual was about 1.86 hours, a new set of light elements was obtained by combining this epoch of minimum light with those from recent literature: H.J.D. MIN.I = 2447804.6739 + 0.93509705dE +-13 p.e. +-36 p.e. Note that this period is about 0.289 seconds shorter than that of Pierce. Table II contains the epochs of minimum light used to get the above light elements, as well as the residuals. Photoelectric epochs of minimum light were weighted by a factor of five in the computations. The residual for AO Camelopardalis was computed based on the light elements of Evans et al. (1985). The insignificance of the residual indicates that the period of AO Camelopardalis has remained constant. The residual for WY Cancri was calculated based on the light elements of Mullis and Faulkner (1988). Mullis and Faulkner presented two times of minimum light that indicated the period had decreased. A time of minimum light presented by Mullis and Faulkner (1989) along with the time of minimum light presented here supports the new period of Mullis and Faulkner (1988). The residual for R Canis Majoris was computed from the light elements of S.A.C. No. 61 (1990). Since the residual was about 48.5 minutes, a new set of light elements was calculated by combining this epoch of minimum with those from recent literature.: H.J.D. MIN.I = 2447918.7189 + 1.13595100dE +-25 p.e. +-258 p.e. Note that this period is about 1.037 seconds longer than that of S.A.C. No. 61. The epochs of minimum light used to get the above light elements, as well as the residuals, are shown in Table III. Photoelectric epochs of minimum light were weighted by a factor of five in the computations. The residuals for SW Lacertae were determined from the light elements of Faulkner et al.(1984). The period of SW Lacertae has apparently remained constant because the residuals presented here are very small. The residuals for XY Leonis were determined from the light elements of Kaluzny and Pojmanski (1982). Because the residuals were about 35 minutes, a new set of light elements was obtained by combining these epochs of minimum light with those from recent literature: H.J.D. MIN.I = 2447864.9125 + 0.28409949dE +-18 p.e. +-27 p.e. Note that this period is 0.219 seconds longer than that of Kaluzny and Pojmánski. The epochs of minimum light used to get the above light elements, as well as the residuals, are given in Table IV. A period change apparently occurred between -4900 and 0 cycles. This explains the large probable errors exhibited by the new light elements presented here. Note the systematic differences between the O-C's for primary and secondary eclipses which indicate a displaced secondary. Faulkner and Grossoehme (1983) noted this, but it was first noted by Gehlich et al.(1972). The residual for AM Leonis was computed based on the light elements of Rafert and Twigg (1980). Since the residuals for AM Leonis presented by Mullis and Faulkner in 1989 and here are relatively small, it can be deduced that the period of AM Leonis had remained constant since the observations of Rafert and Twigg. The residual for GR Tauri was determined from the light elements of Yamasaki et al. (1984). Because their observations only spanned 81 cycles, we attempted to improve the period, using our epoch of minimum light and those of Yamasaki et al: H.J.D. MIN.I = 2444573.1070 + 0.42985160dE +-2 p.e. +-7 p.e. This refined period is only approximately 0.0778 seconds shorter than the period of Yamasaki et al. Table V contains the epochs of minimum light used to get the above light elements. Table I Epochs of Minimum Light Star Hel. J.D. E (O-C) AA Andromedae 2447804.6670 19168.0 -0.0775 AO Camelopardalis 2447864.7879 6423.5 +0.0025 WY Cancri 2447971.6029 2346.0 -0.0004 R Canis Majoris 2447918.7210 22790.0 +0.0337 SW Lacertae 2447821.5405 6968.0 +0.0007 " 2447822.6617 6971.5 -0.0006 " 2447825.7092 6981.0 +0.0001 " 2447850.5649 7058.5 +0.0000 " 2447854.5747 7071.0 +0.0008 " 2447860.5080 7089.5 +0.0008 XY Leonis 2447864.9146 9822.0 +0.0237 " 2447881.8187 9881.5 +0.0240 AM Leonis 2447971.7479 4978.5 -0.0003 GR Tauri 2447881.6752 7697.0 -0.0066 Table II AA Andromedae Hel. J.D. E (O-C) Source 2439033.448 -9380.0 -0.0155 H.B.Z. No. 76(1987) 2441598.443 -6637.0 +0.0082 " 2441599.376 -6636.0 +0.0061 " 2441600.308 -6635.0 +0.0030 " 2441959.374 -6251.0 -0.0082 " 2441960.324 -6250.0 +0.0067 " 2447060.3455 -796.0 +0.0089 B.A.V. Mitt. No. 50 (1988) 2447804.6670 0.0 -0.0073 This paper 2448209.5689 433.0 -0.0020 Faulkner (1991) Table III R Canis Majoris Hel. J.D. E (O-C) Source 2445743.384 -1915.0 +0.0113 B.A.V. Mitt. No. 43 (1986) 2445743.378 -1915.0 +0.0053 " No. 48 (1988) 2446521.493 -1230.0 -0.0061 " No. 52 (1989) 2446536.247 -1217.0 -0.0195 B.B.S.A.G. No. 82(1987) 2447205.330 -628.0 -0.0116 B.A.V. Mitt. No. 50 (1989) 2447230.345 -606.0 +0.0124 B.B.S.A.G. No. 88 (1988) 2447581.339 -297.0 -0.0024 " No. 91 (1989) 2447918.7210 0.0 +0.0021 This paper Table IV XY Leonis Hel. J.D. E (O-C) Source 2445396.6566 -8688.0 +0.0005 Faulkner/Grossoehme (1983) 2445416.6904 -8617.5 +0.0053 " 2445444.6685 -8519.0 -0.0004 " 2445449.6462 -8501.5 +0.0025 " 2445732.8868 -7504.5 -0.0011 Faulkner (1986) 2446079.9122 -6283.0 -0.0032 " 2446469.4080 -4912.0 -0.0078 Pohl et al. (1987) 2447864.9146 0.0 +0.0021 This paper 2447881.8187 59.5 +0.0023 " Table V GR Tauri Hel. J.D. E (O-C) Source 2444544.3075 -67.0 +0.0006 Yamasaki et al. (1984) 2444573.1074 0.0 +0.0004 " 2444578.2643 12.0 -0.0009 " 2444579.1252 14.0 +0.0003 " 2446438.6622 4340.0 -0.0007 Faulkner (1986) 2447881.6752 7697.0 +0.0004 This paper CHRISTOPHER R. MULLIS Astronomy Department University of Virginia Charlottesville, VA 22903-2475 U. S. A. DANNY R. FAULKNER University of South Carolina- Lancaster Lancaster, SC 29720 U. S. A. References: Evans, E.E., Grossoehme, D.H., and Moyer, E.J. 1985, Pub.A.S.P., 97, 648. [BIBCODE 1985PASP...97..648E ] Faulkner, D.R. 1986, Pub.A.S.P., 98, 605. [BIBCODE 1986PASP...98..690F ] -----, 1991, private communication. Faulkner, D.R., and Grossoehme, D.H. 1983, Inf.Bull.Var.Stars, No. 2335. Faulkner, D.R., Evans, E.E., Grossoehme, D.H., and Moyer, E.J. 1984, Inf.Bull.Var.Stars, No. 2473. Gehlich, U.K., Prolss, J., and Wehmeyer R.1972, Astr. and Astrophy. 18, 477. [BIBCODE 1972A&A....18..477G ] Kaluzny, J., and Pojmánski, G. 1982, Inf.Bull.Var.Stars, No. 2181. Mullis, C.R., and Faulkner, D.R. 1988, Inf.Bull.Var.Stars, No. 3206. -----, 1989, Inf.Bull.Var.Stars, No. 3354. Pierce, N.L. 1951, Princeton Contr, 25, 9. Pohl, E., Akan, M.C., Ibanoglu, C., Sezer, C., and Güdür, N. 1987, Inf.Bull.Var.Stars, No. 3078. Rafert, J.B. and Twigg, L.W. 1980, Mon.Not.R.A.S., 193, 79. [BIBCODE 1980MNRAS.193...79R ] Yamasaki, A., Okazaki, A, and Kitamura, M. 1984, Pub.Astro.Soc.Japan, 36, 175. [BIBCODE 1984PASJ...36..175Y ]