First investigations of 14 neglected, late-type contact binaries

Abstract

In the current work we present the first investigations of 14 neglected, late-type, short period contact binaries using period variation, photometric and spectroscopic analysis performed on long term space and ground based observations. The binaries in study belong to spectral classes F to K. In this study the two contact binaries TIC 242100930 and TIC 332918217 are suggestive to be precursors to merger candidates since they showed highest period decreasing rates ∼ 10^‑6 day/yr. Preliminary photometric analysis using PHOEBE revealed 9 of them to be in marginal, 4 in over and 1 in deep contact configuration. The evidence of magnetic activity is observed in 6 of the contact binaries either by presence of spots in their photometric solution or photospheric and chromospheric lines in their spectra from LAMOST/VBT/HCT, suggesting such activity to be an inherent feature in these binaries, irrespective of their evolutionary stages. The equivalent widths of Na and Hα lines, in the spectra taken from VBT and HCT for TIC 7022755 and TIC 20572196, show strong phase dependent variability. Additionally a strong correlation is found between equivalent widths of Na and Hα lines through out the observed phases, for the high mass ratio contact binary TIC 7022755. TIC 50717816 is found to be a deep overcontact binary (f ≥ 50%) with extreme low mass ratio (q ∼ 0.22), showing a long term period decrease, which may further evolve into a progenitor to blue straggler, due to merger of its components. Using the collective results from current study, an attempt is made to explain the evolution of the 14 contact binaries via AML and TRO models.