COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 821 Konkoly Observatory Budapest 1973 August 27 PHOTOGRAPHIC PHOTOMETRY OF BL LACERTAE BL Lacertae was first observed and classified as an optical variable by Hoffmeister (1929). Independently VRO 42.22.01 was observed by MacLeod et al.(1965). In 1968 Schmidt identified BL Lac with the radio source VRO 42.22.01. Since 1968 MacLeod et al.(1971) have been monitoring this variable source at 2.8, 3.75, and 4.5 cm. With the available photographic data, Shen and Usher (1970) report a range in photographic magnitude of 12.4-16.4 for BL Lacertae and that the light curve shows no periodicity. Photoelectric studies by Racine (1970) and by Milone (1972) show irregular rapid variability. Day-to-day variations usually amount from 0.1m to 0.3m. Milone (1972) reported a variation of 0.4m in four minutes. The spectrum of BL Lac reveals one doubtful spectral feature and the distance to the object is essentially unknown (Oke et al. 1969). Bertaud et al.(1973) have constructed a light curve for the period of June, 1968 - January, 1971. A correlation between the color index B-V and the magnitude is reported. Photographic photometry has been obtained for BL Lacertae with the 102-cm Ritchey-Chretien reflector at Prairie Observatory of the University of Illinois. Plates were taken at the f/7.6 Cassegrain focus at irregular intervals during each observing season from September, 1969 to September, 1972. Plate-filter combinations were used to give approximate U, B, and V magnitudes. Kodak 103a-D emulsion behind a Schott GG11 filter (V), Kodak IIa-O, 103-O, or Ia-O emulsion behind a Schott GG13 filter (B), and Kodak IIa-O or 103a-O emulsion behind a Schott UG2 filter (U) were used to obtain the magnitudes. These plates were measured with an Astro Mechanics iris photometer. The photoelectric sequence of Bertaud et al.(1969) was used for forming calibration curves. The internal plate accuracy is approximately +/-0.05 magnitudes for all three colors. Table I contains for each observations: the Julian date to hundredths of a day, and the U, B, or V magnitude. These 1969 Table I UBV Photometry of BL Lacertae JD U B V JD U B V 2440485.72 15.05 2441161.74 15.68 15.88 14.66 2440504.71 15.04 2441164.72 15.34 2440504.73 14.20 2441176.85 15.40 2440825.71 14.59 2441236.59 15.03 2440825.74 13.63 2441236.63 16.22 2440834.82 14.87 2441236.69 17.08 2440834.84 13.86 2441262.60 16.08 2440858.74 14.00 2441262.64 14.50 2440875.72 14.82 2441269.61 16.43 2440875.75 15.32 2441269.65 15.24 2440875.80 13.87 2441278.56 16.06 2440878.63 13.82 2441504.78 15.68 2440885.65 14.85 2441504.80 14.62 2440885.76 15.88 2441541.76 14.69 2440885.79 13.89 2441541.79 15.83 2440889.63 16.88 2441547.75 14.77 2440895.61 15.87 2441547.77 16.03 2440896.60 17.15 2441558.59 14.60 2440896.63 14.78 2441558.61 15.85 2440896.77 15.91 2441570.75 14.13 2440907.58 15.88 2441570.77 15.30 2440907.62 15.68 2441577.65 15.72 2440911.59 13.84 2441577.66 14.93 and 1970 observations support those of Bertaud et al. (1973) and in a few cases supplement certain portions of the light curve not observed by them. The observations obtained during the 1971 and 1972 observing seasons show the same type of irregular behavior observed in the past. Our observations show a B-V, V relation that is consistent with those of others (Bertaud et al. 1973). Our observations introduce more scatter into this relation since our B-V was derived photographically. We are indebted to Dr. E. A. Avner, Dr. E. W. Weis, Mr. B. W. Rust, and Mr. T. V. Smith for obtaining some of the observations. Two of us (G.D. and D.D.) gratefully acknowledge support of departmental assistantships. GRACE L. DEMING, DRAKE DEMING and KENNETH M. YOSS. Department of Astronomy, University of Illinois References: Bertaud, C., Dumortier, B., Veron, P., Wlerick, G., Adam, G., Bigay, J., Garnier, R., and Duruy, M. 1969, Astr. and Ap. 3, 436. [BIBCODE 1969A&A.....3..436B ] Bertaud, C., Wlerick, G., Veron, P., Dumortier, B., Bigay, J., Paturel, G., Duruy, M., and Saevsky, de, P. 1973, Astr. and Ap. 24, 357. [BIBCODE 1973A&A....24..357B ] Cannon, R.D., Penston, M.V., and Brett, R.A. 1971, M.N.R.A.S. 152, 79. [BIBCODE 1971MNRAS.152...79C ] Dupuy, D., Schmidt, J, McClure, R., Bergh, van den, S., and Racine R. 1969 Ap.J. (Letters) 156, L135. [BIBCODE 1969ApJ...156L.135D ] Hoffmeister, C. 1929, A.N. 236, 233. [BIBCODE 1929AN....236..233H ] MacLeod, J.M., Andrew, B.H., Medd, W.J., and Olsen, E.T. 1971, Ap. Letters 9, 19. [BIBCODE 1971ApL.....9...19M ] MacLeod, J.M., Swenson, G.W., Yang, K.S., and Dickel, J.R. 1965, A.J. 70, 756. [BIBCODE 1965AJ.....70..756M ] Medd, W.J., Andrew, B.H., Harvey, G.A., and Locke, J.L. 1972, Mem.R. Astr.Soc. 77, 109. [BIBCODE 1972MmRAS..77..109M ] Milone, E.F., 1972, Pub.A.S.P. 84, 723. [BIBCODE 1972PASP...84..723M ] Oke, J.B., Neugebauer, G., and Becklin, E.E. 1969, Ap.J.(Letters) 156, L41. [BIBCODE 1969ApJ...156L..41O ] Racine, R. 1970, A.J. (Letters) 159, L99. [BIBCODE 1970ApJ...159L..99R ] Schmidt, J.L. 1968, Nature 218, 663. [BIBCODE 1968Natur.218..663S ] Shen, B.S.P. and Usher, P.D. 1970, Nature 228, 1070. [BIBCODE 1970Natur.228.1070S ] Tritton, K.P. and Brett, R.A. 1970, The Observatory 90, 110. [BIBCODE 1970Obs....90..110T ] Visvanathan, N. 1969, Ap.J. (Letters) 155, L133. [BIBCODE 1969ApJ...155L.133V ]