Fundamental Parameters of a Binary System Consisting of a Red Dwarf and a Compact Star

TIC 157365951 has been classified as a delta 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 M 1 = 0.31 +/- 0.01M circle dot and its radius as R 1 = 0.414 +/- 0.004R circle dot. By fitting the double-peaked H alpha emission, we derived the mass ratio of q = 1.76 +/- 0.04, indicating a compact star mass of M 2 = 0.54 +/- 0.01M circle dot. Using Phoebe to model the light curve and radial velocity curve for the detached binary system, we obtained a red dwarf star mass of M 1 = 0.29 +/- 0.02M circle dot, a radius of R 1 = 0.39 +/- 0.04R circle dot, 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 M 2 = 0.53 +/- 0.05M circle dot. Constraining the system to be semidetached gives M 1 = 0.34 +/- 0.02M circle dot, R 1 = 0.41 +/- 0.01R circle dot, and M 2 = 0.62 +/- 0.03M circle dot. 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.