COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2407 Konkoly Observatory Budapest 4 October 1983 HU ISSN 0374-0676 MINIMUM TIMES OF THE ECLIPSING VARIABLES AH Cep AND IU Aur In a paper by one of the present authors (Mayer, 1980) an increasing period was suspected for the early-type eclipsing binary AH Cep, and recently Rafert (1982) suggested an apside-line rotation for this star. In Table I, five new Table I Minima of AH Cep --------------------------------------------------------------------- J.D.hel. Error Epoch O-C Source --------------------------------------------------------------------- 2443779.813 0.011d 4953 +0.028d Hartigan and Binzel (1982) 2444010.532 0.002 5083 +0.028 Skalnate Pleso Observatory 2445200.499 0.002 5753.5 +0.020 Ondrejov Observatory 2445223.570 0.002 5766.5 +0.019 Ondrejov Observatory 2445562.5380 0.0006 5957.5 +0.0073 Ondrejov Observatory +) 2445579.398 0.003 5967 +0.008 Skalnate Pleso Observatory --------------------------------------------------------------------- +) Average of measurements in V, B and U colours, individual measurements are 2445562.5383, .5376 and .5381, respectively. photoelectric times of minima together with a minimum reported by Harridan and Binzel (1982) are given. Except of the minimum on J.D. 2445562, the minima were only poorly covered by observations, and their estimated mean errors are rather large. The table gives also O-C differences from the ephemeris by Guarnieri et al. (1975): Pri.Min. = J.D.hel. 2434989.404 + 1.774759d * E. Together with other photoelectric minima listed by Mayer (1980) the minima from Table I are plotted in Figure 1 (except of the minimum by Huffer and Eggen). Apparently, the new minima do not support any of the mentioned suggestions. The period changes of AH Cep are probably irregular. An increase of the amplitude of AH Cep light curve was observed by Mayer (1980). Now it seems that the amplitude has risen again to about 0.25m (sec. min.) and 0.28m (pri. min.), in V as well as in B colour. Two new minima were measured for IU Aur (see Table II), As discussed e.g. by Eaton (1979), Schaefer (1981) or Mayer (1983), a monotonous increase of amplitude of both minima of this variable lasts for several decades. The observed depths of both minima are given in Table II, they are again deeper [FIGURE 1] Table II Minima of IU Aur ---------------------------------------------------------- J.D.hel. Error Epoch O-C Minima Depth V B U ---------------------------------------------------------- 2445240.5271 0.0010d 3749.5 -0.0018d 0.56m 0.55m 0.57m 2445337.4421 0.0006 3803 +0.0007 0.68 0.68 0.74 ---------------------------------------------------------- now than previously. The O-C differences in the table have been calculated from the ephemeris given by Mayer (1983),: Pri.Min. = J.D.hel. 2438448.4068+1.8114748d*E-0.0066d*sin(2.208dE+25d). PAVEL MAYER Department of Astronomy and Astrophysics, Charles University, Svedska 8, 150 00 Praha 5, Czechoslovakia JOZEF TREMKO Astronomical Institute of the Slovak Academy of Sciences, 059 60 Tatranska Lomnica, Czechoslovakia References: Eaton, J.A.: 1979 Inf.Bull.Var. Stars No. 1614 Guarnieri, A., Bonifazi, A., Battistini, P.: 1975, Astron. Astrophys. Suppl. 20, 199 [BIBCODE 1975A&AS...20..199G ] Hartigan, P., Binzel, R.P. 1982, Journ. AAVSO 11, 21 [BIBCODE 1982JAVSO..11...21H ] Mayer, P.: 1980, Bull.Astr.Inst. Czechoslovakia 31, 292 [BIBCODE 1980BAICz..31..292M ] Mayer, P.: 1983, Bull.Astr.Inst. Czechoslovakia 34, in print [BIBCODE 1983BAICz..34..335M ] Rafert, J.B.: 1982, Publ.Astr.Soc. Pacific 94, 485 [BIBCODE 1982PASP...94..485R ] Schaefer, B.E.: 1981, Publ.Astr.Soc. Pacific 93, 225 [BIBCODE 1981PASP...93..225S ]