Observation And Investigation On Eclipsing Am Binaries

Eclipsing Am binaries are the eclipsing binaries consisting of Am type chemically peculiar star.Chemically Peculiar Stars(CP stars)are the stars with abnormal strong or weak spectral lines of some elements, the formation and evolution of which are always open questions in astrophysics. Most CP stars are main sequence A and B type stars. The main classification of CP star should be Am star, magnetic CP star, Hg-Mn star and He-abnormal star. CP stars also consist of some triple even quadruple systems. Am star shows the highest binaries percentage(up to 90% or higher), and many Am stars are found in eclipsing binaries. As we all know, eclipsing binary is a significant way to obtain the fundamental physical parameters of stars, such as mass,radius and others,so photometric observation and analysis of eclipsing Am binaries can derive the physical parameters,mass transfer and other information of Am star, which will promote the investigation of CP stars effectively. A brief overview and research progress of CP stars were given in this paper. In 2009, Renson & Manfroid reported a catalogue of Am and Ap stars with 73 eclipsing Am binaries inside.Basing on this,we make investigation and survey about the eclipsing Am binaries, and obtain a more complete catalogue of eclipsing Am binaries currently.Two eclipsing Am binaries with periods shorter than 1 day were chose as our targets: V1073 Cyg and TYC6408-989-1. According to the result of investigation and combining with the observation light curves and the orbital analysis, the conclusions are shown as follow:1. We made a supplement to the catalogue of eclipsing Am binaries referring to the correlatable papers so far, another 17 eclipsing Am binaries were found and listed in the supplement table with period and spectral type. The statistical analysis about the periods of eclipsing Am binaries showed that the peak of the periods distribution was 2-4 days, which concentrative distributed in 2-3 days.Few binaries' periods were longer than 20 days or shorter than 1 days. There are only four systems with period in 1 days: TYC6408-989-1, V1073 Cyg, V2787 Oriand IW Per, and IW Per comes from the supplement catalogue of eclipsing Am binaries.2.For the W Uma type eclipsing Am binary V1073 Cyg, photometric observation together with the analysis of light curve and orbital period lead to that the orbital period of V1073 Cyg is decreasing continuously with?P =-4.91(±0.93) ×10-8d yr-1superposed by a cyclic change. The period decrease can be caused by the synthetical effect of mass transfer between the components and angular momentum loss. The cyclic change, of which the period is 84.52(±0.52)yrand the semi-amplitude is 4.95(±0.42)AU, can be explained by the swing of binary's barycenter due to the existence of a third body with M3= 0.488(±0.048)M.Light curve analysis revealed that V1073 Cyg is an over-contact system and about20% of the total luminosity comes from the third body. The light curve analysis was consistent with the O- C theoretical analysis for the third body very well,so we confirm that V1073 Cyg should be a triple system.3.The light curve of TYC6408-989-1 is EB type. For the first detailed photometric observation and investigation of this system, integrated V band light curve was acquire by the 70 cm telescope in Li-jiang station. The analysis of light curve can be carried out with W-D program in three modes, and the mass ratio was in the range of 0.205-0.274. We can conjecture that TYC6408-989-1 may be a near contact binary. Further efforts will be made to require more observation data in multiple bands of this system, so that we can accomplish more detailed investigation about this system.