COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3401 Konkoly Observatory Budapest 8 December 1989 HU ISSN 0374 - 0676 TWO - COLOUR - LIGHTCURVE AND PRELIMINARY ELEMENTS FOR AL Leo BAV-Mitteilung Nr. 53 AL Leo = SAO 098873 = BD+18d2297 (9.1) = 354.1934 = CSV 1536 = P 3369 was discovered by Hoffmeister (1934) as probably rapidly changing eclipsing binary star. Sandig (1947) reported, that on 80 plates he inspected, only two minima were found. The variable was also investigated by Kurochkin (1948), who reported 14 photo- graphic brightness measurements and derived from them first elements with a period of 4.1444d and a range of brightness between 10.1m and 10.5m. These elements were confirmed by Vasilyanovskaya (1955), who corrected the epoch by -0.185p and the limits of lightchange to 10.28m - 10.70m. The small extent of the observational material made us put AL Leo on our program. AL Leo was observed during 15 nights in spring and autumn 1989 in B and V magnitudes with a single-channel photometer (which utilizes an uncooled EMI 9781 B photomultiplier tube). The telescope used was a 0.35 m Schmidt-Cassegrain at the private Observatory of one of us, which operates fully automatically. For a description see Agerer (1988). SAO 098898 = BD+18d2306 was chosen as a comparison star and SAO 098890 = BD+18d2302 was used Table 1. Observed times of minima for AL Leo, epochs and residuals computed with respect to the ephemeris derived in this paper No. JD helioc. Min Type Epoch (O-C) Source 1 2419829.36 I p:: -17437 +0.092 Kurochkin (1948) 2 20894.47 II p -16773.5 -0.057 3 26116.39 I p -13521 -0.071 4 2447609.473 I E: -134 +0.0041 Agerer 5 47613.4941 II E -131.5 +0.0032 6 47654.429 I E -106 -0.0025 7 47824.619 I E 0 +0.0030 p denotes pg plate min.(weight 2), E photoelectrical min.(weight 100 or 25). The minimum marked ":" received reduced weight, while those marked "::" were discarded. [FIGURE 1] Differential B and V light and B-V colour curves of AL Leo. to check its constancy. Measurements showed that the differences in magnitude between comparison and check star were constant at (comparison - check) Delta V = 0.135m +-0.046m Delta (B-V) = -0.395m +-0.041m Instrumental magnitude differences were converted to the international UBV-System by observations of 27 LMi and 28 LMi. Our observations showed AL Leo to be a short-period Algol-type eclipsing variable (EA). The depth of the secondary minimum differs only marginally from that of the primary. Moreover, many measurements were made at large zenith distances and under not always satisfying atmospheric conditions. Therefore the variations between observations where the light ought to be constant are of the same order as the difference between primary and secondary eclipse brightness. Further observations are recommended and planned in order to confirm the relation of primary to secondary minimum and to improve the ephemeris. Little or no colour change could be detected during all phases. From our observations we derive the following preliminary elements: Min I = 2447824.616 + 1.605514d * E +/-1 +/-1 F. AGERER D. LICHTENKNECKER Berliner Arbeitsgemeinschaft fuer Veranderliche Sterne e.V. (BAV) Munsterdamm 99, D-1000 Berlin 41 References: Agerer, F.: 1988, BAV Rundbrief 37(2), 60 Hoffmeister, C.: 1934, Astron. Nachrichten 253, 196 [BIBCODE 1934AN....253..195H ] Kurochkin, N.E.: 1948, Variable Stars (Moscow), 6, 303 [BIBCODE 1949PZ......6..303K ] Sandig, H.-U.: 1947, Astron. Nachrichten 275, 37 [BIBCODE 1947AN....275...37S ] Vasilyanovskaya, O.P.: 1955, Astron. Tsirk. No. 164, 19