COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 3953 Konkoly Observatory Budapest 22 November 1993 HU ISSN 0374 - 0676 1992 PHOTOMETRY OF UZ LIBRAE Heckert and Hickman (1991) and Heckert (1992) report light curves of UZ Librae (= #102 in the catalog of Strassmeier et al. 1988) from 1988 to 1991. Grewing et al. ( 1989) deduce properties of the components and the period. I present new photometry on 12, 13, 20 and 27 May, 25 July, and 3, 4, and 10 August 1992. I used the San Diego State University 24 inch telescope at Mount Laguna Observatory. During May the photometer was equipped with a Hamamatsu GaAs phototube and UBVRI filters. During July and August this tube was replaced with a less red sensitive EMI 9789 tube equipped with UBV filters only. The data are transformed to the standard Johnson-Cousins UBVRI system. The comparison and check stars are BD -07d 4044 and BD -08d 3998. The check star data show no systematic differences between the transformed data taken with the different tubes. Following Grewing et al. (1989) I computed the orbital phase using: phi=2445428.88 + 4.767885 E. TABLE 1 ----------------------------------------------------------------- Julian Day Phase DeltaU DeltaB DeltaV DeltaR DeltaI ----------------------------------------------------------------- 2448754.893 0.587 -0.614 -0.352 -0.316 -0.340 -0.416 2448755.875 0.793 -0.605 -0.341 -0.309 -0.341 -0.423 2448762.840 0.253 -0.598 -0.357 -0.316 -0.350 -0.419 2448769.814 0.716 -0.587 -0.315 -0.280 -0.311 -0.391 2448828.714 0.070 -0.586 -0.335 -0.298 2448837.679 0.950 -0.624 -0.335 -0.300 2448838.726 0.169 -0.616 -0.346 -0.314 2448844.673 0.417 -0.746 -0.449 -0.399 ----------------------------------------------------------------- Table 1 shows the differential magnitudes in the sense star - comparison, and the B and V light curves are in Figure 1. The light curves show a double peaked structure similar to the 1988 to 1990 light curves, but with the larger and smaller maxima interchanged (Heckert and Hickman 1991 and Heckert 1992). The single peaked light curve in 1991 seems to be a transition stage where the larger and smaller maxima are switching places. In terms of the spot structure, I [FIGURE 1] Figure 1. UZ Librae - 1992 interpret these data as showing the larger spot at roughly phase 0.1 to 0.2 and the smaller spot at roughly phase 0.5 to 0.6 from 1988 to 1990. In the transition year, 1991, the spot at phase 0.1 to 0.2 had broken up, leaving only the spot at phase 0.6. In 1992 this spot became the larger spot at roughly phase 0.7 and a smaller spot reappeared at roughly phase 0.0 to 0.1. Ron Angione scheduled very generous amounts of time on the Mt. Laguna 24" telescope for this work. The Research Corporation provided support for this work. PAUL A. HECKERT Western Carolina University Cullowhee, NC 28723 USA References: Grewing, M., Bianchi, L., and Garrido, R.: 1989, Astron. and Astrophys., 223, 172 [BIBCODE 1989A&A...223..172G ] Heckert, P.A. and Hickman M.A.: 1991, Inf. Bull. on Var. Stars, No. 3570. Heckert, P.A.: 1992, Inf. Bull. on Var. Stars, No. 3796. Strassmeier, K. G., Hall, D. S., Zeilik, M., Nelson, E., Eker, Z., and Fekel, F. C.: 1988, Astron. and Astrophys. Suppl. Ser., 72, 291 [BIBCODE 1988A&AS...72..291S ]