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We identify the bright Am-type star HD 181793 to be a previously-unknown eclipsing, chemically peculiar heartbeat binary, the second of its kind known. The system carries an orbital period of P = 11. 47578275 0. 00000055 days. We use TESS photometry and LCOGT NRES radial velocity data to build a self-consistent orbital model and determine the fundamental stellar characteristics of the primary. We use a spectral separation method to unveil the secondary and measure the masses of both stars. The radial velocity amplitude of the primary, K₁ = 47. 41+0. 13-0. 12 km s^-1, gives a mass M₁ = 1. 57 0. 01 Msun. The secondary radial velocity amplitude K₂ = 84. 95+0. 12-0. 09 km s^-1 yields a mass ratio q = 0. 558 0. 002 and a secondary mass M₂ = 0. 87 0. 01 Msun. From the spectral energy distribution and Gaia parallax we find a radius R₁ = 2. 04 0. 05 Rsun. The grazing transit profile and spectroscopic luminosity ratio indicate R₂ = 1. 04+0. 15-0. 10 Rsun, suggesting an early-K spectral type. We show that the heartbeat feature in the TESS light curve can be explained by time-varying ellipsoidal variation, driven by the orbital eccentricity of e = 0. 3056+0. 0024-0. 0026, and relativistic beaming of the light of the primary. We find no evidence of tidally-excited oscillations.
Uronen et al. (Tue,) studied this question.