COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2862 Konkoly Observatory Budapest 11 February 1986 HU ISSN 0374 - 0676 AX URSAE MAJORIS The elements of AX Ursae Majoris, an RR Lyrae variable (RRab) discovered in 1958 (Romano, 1958) in the field of Chi Ursae Majoris, were published in 1964 (Romano, 1964). The ephemeris: Max. = 2435951.354 + 0.53510d*E (1) satisfied the photographic observations taken during the period March 1957 - May 1963. In a recent GEOS note, Boninsegna (1985) determined new elements of this star considering only the visual estimates of three GEOS observers Table I max. E O-C max. E O-C 24... 24... 38737.637 5207 +0.070d 42541.549 12317 +0.057d 849.431 5416 +.039 870.504 12932 +.017 39201.432 6074 -.015 43161.521 13476 +.014 323.389 6302 -.047 191.544 13532 +.079 448.573 6536 -.060 459.513 14033 +.035 614.477 6846 -.016 512.488 14132 +.049 40270.465 8072 +.034 688.462 14461 +.024 326.556 8177 .051 966.532 14981 -.078 416.419 8345 -.071 986.446 15018 +.043 563.567 8620 -.051 44017.484 15096 +.059 621.395 8728 -.004 203.570 15424 -.019 943.443 9330 -.030 406.420 15803 +.089 41057.438 9543 +.009 668.498 16293 +.050 119.450 9659 -.038 45029.484 16968 -.040 302.462 10001 +.004 417.459 10216 -.023 45074.440 17052 -.017 42044.513 11388 +.025 075.522 17054 -.005 066.381 11429 -.041 382.563 17628 -.009 120.417 11530 -.038 402.355 17665 -.008 158.537 11601 +.098 406.622 17673 -.020 190.533 11661 -.004 698.689 18219 -.016 373.532 12003 +.032 809.409 18426 -.022 511.527 12261 +.004 818.524 18443 -.001 [FIGURE 1] [FIGURE 2] Table II m phase n m phase n 13.70 0.730 13 13.03 0.173 8 13.79 .768 10 13.18 .225 17 13.50 .827 14 13.25 .276 9 13.14 .875 16 13.40 .321 10 12.56 .915 12 13.53 .375 10 12.32 .975 11 13.56 .451 20 12.41 .251 10 13.73 .546 21 12.45 .702 12 13.65 .623 12 12.71 .127 11 13.59 .665 11 (ten maxima between J.D. 2445074 and 2445818) but the period derived by him does not agree with the observations made during the years 1958- 1964. A continuous survey of the Chi Ursae Majoris field made at Asiago Astrophysical Observatory with the Schmidt telescopes (67/90/210 cm and 40/50/100 cm) during the period May 1964 - December 1983 produced 227 photographic plates (103aO+GG13). These plates were used for determining the magnitudes of this variable star. Using the list of the observed maxima (also those of Boninsegna) I derived the variation of the O-C using the elements (I). In some cases it exceeded the double of the period. Figure I gives the O-C curve. As one can see in this figure, the period of AX UMa had remained nearly constant over the first 5000 epochs, then it decreased continuously. Analysing the O-C curve I derived the following new improved elements that were valid for the interval between J.D. 2438522- 2445818: Max. = 2435951.441 + 0.5351002d*E - 0.52*10^-8*E^2 The average light curve is shown in Figure 2 and Table I lists all the maxima, the epochs and the residuals obtained with the new elements. Table II lists the magnitudes, the phases and epochs plotted in Figure 2. G. ROMANO Istituto di Astronomia, Universita di Padova, Padova, Italy References: Boninsegna, R., 1985, GEOS Circ. RR8, May, 1985. Romano, G., 1958, Specola Ariel, Pub: n. 12. Romano, G., 1964, Specola Ariel, Pub: n. 33.