COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 1446 Konkoly Observatory Budapest 1978 July 3 PECULIARITIES OF SOME Beta LYRAE-TYPE STARS AND THE NEED OF THEIR FURTHER INVESTIGATION During recent years an extensive study of beta Lyrae-type binaries was performed in order to study mass transfer between the components. As change in the orbital period is one of the important features of the systems in which mass transfer occurs we performed a study of this phenomenon. As a result of our research several O-C diagrams were constructed and the parabolic shape of the O-C curve was found. This suggests monotonous mass transfer when mass loss from the system is not taken into consideration. In some cases short term or secular deviations from this course may exist. This gives evidence for nonstationary processes in mass transfer. As the study of nonstationary processes in the evolution and physics of Beta Lyrae-type stars is very important, we prepared a list of those stars with peculiarities in the shape of the O-C curve. The list below contains some of the Beta Lyrae-type stars on the northern hemisphere brighter than ca 11th magnitude in maximum light with observed irregularities of period change. The Table also includes some stars for which reliable data do not exist. For the investigation of the system the photoelectric observations of times of minimum are highly desirable. Table 1 Star name Range of the light period Reason for the variations investigation DS And 10.8 - 11.4 1d010 Gaps in the observations. Light curve and elements desirable V337 Aql 8.7 - 9.7 2.734 Massive components, variations in the light curve. V609 Aql 11.7 - 12.4 0.797 Change in period ? Gap in the observations AP Aur 10.9 - 11.4 0.569 Large changes in period ? EP Aur 10.8 - 11.3 0.591 Shortening of period TX Cas 9.2 - 9.8 2.927 Period changes ? Gap in the observations IR Cas 10.8 - 12.1 0.681 Large change in period ? QQ Cas 10.5 - 11.1 2.142 Period variations WY Cep 10.7 11.6 1.249 Gap in the photoelectric observations XZ Cep 8.4 - 9.2 5.970 Gap in the observations AH Cep 6.9 - 7.1 1.775 Large changes in the period CQ Cep 8.9 - 9.4 1.621 WR component EY Cep 10.1 - 10.7 5.517 No photoelectric observations V366 Cyg 10.0 - 10. 5 1.096 Gap in the observations V367 Cyg 7.4 - 8.0 18.597 Important from the point of evolution V388 Cyg 9.7 - 10.3 0.859 Great period change V680 Cyg 10.2 - 10.9 1.199 Period not correct. No phe observations V729 Cyg 10.6 - 10.9 6.598 Asymmetry of the light curve V885 Cyg 9.9 - 10.3 1.695 Gap in the observations RZ Dra 10.0 - 10.9 0.551 Period change. Asymmetry of the light curve. Secular terms in O-C curve ? TT Her 9.7 - 10.5 0.912 Shortening of the period VY Lac 10.2 - 11.0 1.036 Changes in the period started recently ? AW Lac 10.6 - 11.3 1.143 Gap in the phe observations TZ Lyr 10.4 - 11.4 0.529 Change in the period AN Tau 10.3 - 11.2 1.615 Large change in the period ? V Tri 10.9 - 11.9 0.585 No phe observations AG Vir 8.8 - 9.4 0.643 Changes in the period. Asymmetry of minima AX Vir 10.3 - 10.9 0.703 Few observations J.M. KREINER J. TREMKO Astronomical Laboratory Astronomical Institute of the Institute of Physics Slovak Academy of Sciences Silesian University Tatranska Lomnica Katowice, Poland Czechoslovakia