First photometric investigation of the near-contact binary LM And

Abstract

LM And is a neglected close binary system with a period about 18 h. First complete multi-colors CCD light curves are presented which reveals that LM And is β Lyrae-type eclipsing binary. By analyzing two spectrums, we determined its spectral type of F6 for this binary. Photometric solutions of the binary were obtained by analyzing our multi-colors light curves and the TESS Light curve with the Wilson–Devinney method. The orbital inclination is about 84 degree revealing that the binary is a total eclipsing system. The mass ratio is determined to be about 0.54 and 0.58 for two sets of light curves. It is discovered that LM And is a semi-detached near-contact binary where the secondary component is filling the critical Roche lobe, while the primary is more than 90% filling its Roche lobe. A period investigation suggests that the orbital period of the binary is increasing continuously at a rate of dP/dt=4.2(±0.6)×10−7days/year, which may be attributed to mass transfer from the less-massive component, which fills its Roche-lobe. Therefore, LM And with period increasing will evolve into the contact configuration.