2024AJ....168..217D

TIC 157365951 has been classified as a δ Scuti type by the International Variable Star Index. Through the spectra from Large Sky Area Multi-Object Fiber Spectroscopic Telescope and its light curve, we further discovered that it is a binary system. This binary system comprises a red-dwarf star and a compact star. Through the spectral energy distribution fitting, we determined the mass of the red dwarf star as M₁ = 0.31 ± 0.01M_⊙ and its radius as R₁ = 0.414 ± 0.004R_⊙. By fitting the double-peaked Hα emission, we derived the mass ratio of q = 1.76 ± 0.04, indicating a compact star mass of M₂ = 0.54 ± 0.01M_⊙. Using Phoebe to model the light curve and radial velocity curve for the detached binary system, we obtained a red dwarf star mass of M₁ = 0.29 ± 0.02M_⊙, a radius of R₁ = 0.39 ± 0.04R_⊙, and a Roche-lobe filling factor of f = 0.995 ± 0.129, which is close to the f = 1 expected for a semidetached system. The Phoebe model gives a compact star mass M₂ = 0.53 ± 0.05M_⊙. Constraining the system to be semidetached gives M₁ = 0.34 ± 0.02M_⊙, R₁ = 0.41 ± 0.01R_⊙, and M₂ = 0.62 ± 0.03M_⊙. The consistency of the models is encouraging. The value of the Roche-lobe filling factor suggests that there might be ongoing mass transfer. The compact star mass is as massive as a typical white dwarf.