COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2570 Konkoly Observatory Budapest 3 August 1984 HU ISSN 0374-0676 A NEW PERIOD CHANGE OF 44i BOOTIS IN 1979* Seven infrared light curves (lambda = 2.25 micron) of the contact binary 44i Bootis were obtained in April 1980 included five complete curves secured on a single night. The 585 individual observations will be published and fully discussed elsewhere (Lunel et al., 1984). The comparison of the new curves (April 1980) with the curves of March 1978 published by Bergeat et al., (1981) led us to the conclusion that the period should have changed during the meantime. Heliocentric epochs were computed by the method of Kwee and van Woerden (1956): Table I Night Hel. J.D. O-C in days (1980 April) Prim.min. (elements of (new elements (2444300+) Duerbeck 1975) this paper) 19-20 49.39044 +0.0034 +0.0011 21-22 51.53145 +0.0019 -0.0005 24-25 54.47726 +0.0017 -0.0006 25-26 55.55004 +0.0032 +0.0009 26-27 56.35231 +0.0020 -0.0003 The O-C diagram for primary minima is given in Figure 1 which includes our infrared data of March 1978 (triangles, observations published by Bergeat et al., 1981) and the above-mentioned results (squares). Minimum times observed by Hopp et al., (1977), Duerbeck et al., (1978) Duerbeck (1978), Margrave (1980, 1982) Mikolajewska and Mikolajewski (1980), Pohl and Gulmen (1981) Rovithis and Rovithis-Livaniou (1981), Hopp and Witzigmann (1982) and Robb and Milone (1982) are denoted by dots. Despite the wide scatter observed around JD 2443600, it is clear that some period change should have occurred between this former value and JD 2444350. As a weighted mean of the available data, we propose the following elements: 2443944.9851 + 0.2678174d E. *The observations were done at the Observatoire de Haute-Provence (CNRS). [FIGURE 1] Figure 1 The diagram of O-C (in days) for primary minima against the heliocentric epoch, as recently observed in the contact binary 44i Bootis. Much more data is needed so as to improve these provisional elements. We note that the new period lengthening (i.e. + 15 x 10^-7 day) has an amplitude comparable to the previous one reported by Bergeat et al., (1972). Presumably the period change occurred in 1979. It is noteworthy that Hopp and Witzigmann (1982) reported an active phase of i Bootis in 1979, while 1978 and 1981 would have been more quiet. Finally the authors wish to emphasize the necessity of having recent and accurate elements at hand when studying features of light curves such as asymmetries. An undetected recent change of small amplitude on the period result in spurious asymmetries. In particular, the odd sine term b2 becomes detectable. Acknowledgements: It is a pleasure to thank the staff of the Observatoire de Haute-Provence. (CNRS) for efficient assistance during observing time. J. BERGEAT M. LUNEL R. GARNIER Observatoire de Lyon 69230 Saint Genis Laval France References: Bergeat, J., Lunel, M., Sibille, F., Van't Veer, F., 1972, Astron. and Astrophys. 17, 215 [BIBCODE 1972A&A....17..215B ] Bergeat, J., Van't Veer, F., Lunel, M., Garnier, R., Sibille, F., Roux, S., 1981, Astron. and Astrophys., 94, 350 and Suppl. 43, 257 [BIBCODE 1981A&AS...43..257B ] Duerbeck, H.W., 1975, Inf.Bull.Var. Stars No. 1023 Duerbeck, H.W., 1978, Astron, and Astrophys. Suppl. 32, 361 [BIBCODE 1978A&AS...32..361D ] Duerbeck, H.W., Karimie, M.T., Hopp, U., Kiehl, M., Witzigmann, S., 1978, Inf.Bull.Var. Stars No. 1497 Hopp, U. Witzigmann, S., Kiehl, M., 1977, Inf.Bull.Var. Stars No. 1353 Hopp, U., Witzigmann, S., 1982, Astrophys. Sp, Sci., 83, 171 [BIBCODE 1982Ap&SS..83..171H ] Kwee, K.K., van Woerden, H., 1956, Bull.Astr.Inst. Netherl. 12, 327 [BIBCODE 1956BAN....12..327K ] Lunel, M., Bergeat, J., Garnier, R., 1984, submitted to Astron. and Astrophys. [BIBCODE 1985A&AS...61...27L ] Margrave, T.E., 1980, Inf.Bull.Var. Stars No. 1869 Margrave, T.E. 1982, Inf.Bull.Var. Stars No. 2086 Mikolajewska, J., Mikolajewski, M., 1980, Inf.Bull.Var. Stars No. 1812 Pohl, E., Gulmen, O., 1981, Inf.Bull.Var. Stars No. 1924 Robb, R.M., Milone, E.F., 1982, Inf.Bull.Var. Stars No. 2187 Rovithis, P., Rivithis-Livaniou, H., 1981, Astrophys. Sp. Sci., 76, 351 [BIBCODE 1981Ap&SS..76..351R ]