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+0.13−0.12kms−1, gives a mass M1=1.57±0.01 Msun. The secondary radial velocity amplitude K2=84.95+0.12−0.09kms−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.
@article{arxiv.2406.12786,
title = {Dynamical mass determination and partial eclipses of the heartbeat star HD 181793},
author = {Laura E. Uronen and Andrew Collier Cameron and Thomas G. Wilson},
journal= {arXiv preprint arXiv:2406.12786},
year = {2024}
}