Long-period double-lined eclipsing binaries: the system V454 Aur with the secondary eclipse caused by the occultation of the hotter component

Abstract

We present the results of our study of the long-period eclipsing binary star \Aur. The results are based on spectroscopic data obtained with the UFES \'echelle spectrograph and photometric observations from TESS. The derived radial velocity curve is based on 17 spectra obtained between 2021 and 2023, covering all orbital phases of this binary system. The orbital period determined from TESS data, $P = 27.019803 \pm 0.000003$ days, agrees within uncertainties with the period established in previous studies. The model constructed for the TESS photometric light curve achieves a precision of 0.01\%. The effective temperatures of both components, as well as the system metallicity, were directly derived from the spectra and are $T_\mathrm{eff, A} = 6250 \pm 50$\,K, $T_\mathrm{eff, B} = 5855 \pm 50$\,K, and $\mathrm{[Fe/H]} = -0.10 \pm 0.08$, respectively. Our analysis of the photometric and spectroscopic data allowed us to directly compute the luminosities of the components, $L_A = 1.82\,L_\odot$ and $L_B = 1.07\,L_\odot$, their radii, $R_A = 1.15\,R_\odot$ and $R_B = 1.00\,R_\odot$, and their masses, $M_A = 1.137\,M_\odot$ and $M_B = 1.023\,M_\odot$, with uncertainties below 1\%. Comparison with evolutionary tracks indicates that the system's age is $1.18 \pm 0.10$\,Gyr, and both components are still on the main sequence. The \Aur\ system is particularly interesting due to the partial eclipse of the primary component, which results in the ``inversion'' of the primary and secondary minima in the photometric light curve.