COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 3295 Konkoly Observatory Budapest 23 February 1989 HU ISSN 0374 - 0676 PHOTOMETRY OF UU HERCULIS: 1986-88 UU Her is an F supergiant, located at high galactic latitude. It is the prototype of the so-called UU Her variables (Sasselov 1984). The star was well known because of its supposed period switches, i.e. it changed its period in a very short time from ~45 d to ~ 72 d or vice versa. An analysis of visual observations made between 1922 and 1939 showed, however, that the variation of UU Her could be described by (at least) two periods: 72.9 d and 45.3 d [FIGURE 1] Table I J. D. V B-V U-B 2446466.639 8.908 0.393 0.241 6560.540 8.720 .367 .242 6678.342 9.074 .648 .356 6679.347 9.096 .652 .360 6853.653 8.621 .261 .551 6910.539 9.237 .692 .526 6925.483 9.154 .518 .354 6942.422 8.902 .546 .315 6966.413 9.391 .622 .329 6983.378 8.884 .449 .302 6984.383 8.824 .459 .304 6988.405 8.906 .521 .336 6991.429 8.926 .540 .359 7016.392 9.036 .443 .274 7207.637 8.998 .555 .334 7208.609 9.014 .556 .337 7277.538 9.079 .471 7288.507 8.926 .463 .300 7290.496 8.954 .482 .303 7906.442 9.099 .675 .425 7334.491 8.801 .436 .253 7335.468 8.808 .435 .282 7349.355 8.913 .582 .289 .365 8.885 .564 .358 7363.522 9.088 .555 .241 7371.376 8.925 .398 .257 7372.344 8.914 .409 .273 7374.329 8.922 .447 .307 7375.353 8.936 .444 .269 7406.308 9.279 .655 .409 7409.327 9.251 .612 .365 7449.268 9.263 .627 .335 2447450.270 9.263 0.630 0.303 (for details see Zsoldos and Sasselov 1989). These periods are probably always present in the light curve, though with varying amplitude. Photoelectric photometry of UU Her is very important to decide if there are more periods, and to arrive at more precise values of the periods. Recent photometry of the star was made by Fernie (1986), Sasselov et al. (1987) and Umana et al. (1988). Here we present more observations of the variable, made during 1986-88. Table II Year Colour A0 A1 A2 1987 V 9.06 0.26 0.48 B-V 0.56 0.04 0.26 U-B 0.35 0.08 0.22 1988 V 9.06 0.14 0.30 B-V 0.56 0.09 0.21 U-B 0.33 0.06 0.10 UU Her was observed with the 0.5-m and 1-m telescopes of Konkoly Observatory, at Piszkesteto. The comparison stars were those used by Sasselov et al. (1987). Table I lists the observations, these were transformed into the UBV system in the usual way. The light and colour curves of UU Her are plotted in Figure 1 (the triangles are the y measurements of Umana et al. 1988). These curves were fitted with the two periods mentioned above, the fits are also shown in Figure 1 as continuous lines (the two years, 1987 and 1988, were treated separately because of the amplitude change). The amplitudes of the periods are given in Table II for each colour (A1 and A2 are the amplitudes of the longer and shorter periods, respectively, A0 is the mean magnitude). Figure 1 and Table II confirm the conclusion of Umana et al. (1988) - the dominant period now is the shorter one (45.3 d), its amplitude, however, is already decreasing. E. ZSOLDOS and J. JURCSIK Konkoly Observatory Budapest XII, P.O.Box 67 1525 HUNGARY References: Fernie, J.D. 1986, Ap.J. 306, 642 [BIBCODE 1986ApJ...306..642F ] Sasselov, D. 1984, Ap.Space Sci. 102, 161 [BIBCODE 1984Ap&SS.102..161S ] Sasselov, D., Zsoldos, E., Fernie, J.D., Arellano Ferro, A. 1987, PASP 99, 967 [BIBCODE 1987PASP...99..967S ] Umana, G., Catalano, S., Marilli, E., Trigilio, C. 1988, IBVS No. 3144 Zsoldos, E., Sasselov, D. 1989, in preparation