Detection of Four Intermediate-mass Stars with Cool Companions in Low Mass Ratio Eclipsing Binaries

Abstract According to the core fragmentation and dynamical capture theories of binary formation, binaries tend to form with nearly equal masses. The detection of intermediate-mass binaries with low mass ratios challenges these theories, as such binaries may form via disk fragmentation and are very important to investigate binary formation and evolution. However, there are few confirmed samples to robustly test theories of the formation and evolution of binaries due to observational challenges. The development of high-precision space telescopes brings opportunities to study such samples. Based on TESS data, we present the first study on four intermediate-mass eclipsing binaries with the Wilson–Devinney method, which are: TIC 283881816, TIC 343757299, TIC 72444347, and TIC 353077789. All are totally detached eclipsing binaries with q &lt; 0.4. TIC 283881816, TIC 343757299, and TIC 72444347 are A-type binaries with mass ratios of q = 0.34, 0.28, 0.39, respectively. TIC 353077789 is a B-type binary with an extremely low mass ratio of q = 0.18. These low mass ratio systems imply that they are highly likely to be formed via disk fragmentation and will undergo a common envelope evolution. Particularly, TIC 72444347 with a period of 4 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">d</mml:mi> </mml:mrow> </mml:mover> </mml:math> 4 still shows an eccentric orbit, while TIC 343757299 with a longer period (5 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">d</mml:mi> </mml:mrow> </mml:mover> </mml:math> 8) does not, which poses a challenge to the Kraft break. By plotting these components in the H-R diagram, it hints that all systems are main-sequence (MS) primaries with pre-MS companions. They are valuable targets for testing theories of binary formation and evolution.