2019A&A...622A.114H

Aims. We present results of the combined photometric and spectroscopic analysis of three detached eclipsing binaries, the secondary components of which are not visible or are very hard to identify in the optical spectra - ASAS J052743-0359.7, ASAS J065134-2211.5, and ASAS J073507-0905.7. The first one is the known visual binary ADS 4022, and we found that it is a quadruple system composed of two spectroscopic binaries, one of which shows eclipses. None of the systems have previously been recognized as a spectroscopic binary.
Methods. We used the following telescopes/spectrographs to collect a number of high-resolution optical and IR spectra: Subaru/IRCS, CTIO-1.5m/CHIRON, Euler/CORALIE, MPG-2.2m/FEROS, OAO-188/HIDES, and TNG/HARPS-N. We used these data to calculate radial velocities (RVs) and later combined them with MITSuME and ASAS photometry. The Subaru/IRCS IR spectra were crucial for secure identification of the lines of the cooler components. Radial velocity measurements were made with the TODCOR technique, and RV curves were modelled with our own procedure V2FIT. Light-curve modelling was performed with JKTEBOP and PHOEBE codes. Temperatures and metallicities of two systems were estimated from spectra. For the ADS 4022 system we also used the archival WDS data and new SOAR observations in order to derive the orbit of the visual pair for the first time. Ages were estimated by comparing our results with PARSEC isochrones.
Results. The eclipsing pair ASAS J052743-0359.7 A (P=5.27d) is composed of a 1.03(6)M_☉, 1.03(2)R_☉ primary and a 0.60(2)M_☉, 0.59(2)R_☉ secondary. The components of the P=21.57d non-eclipsing pair B likely have masses in between the two eclipsing components, and both pairs are on a ∼188 yr orbit around their common centre of mass. The system ASAS J065134-2211.5 (P=8.22d) consists of a 0.956(12)M_☉, 0.997(4)R_☉ primary and a 0.674(5)M_☉, 0.690(7)R_☉ secondary. Finally, ASAS J073507-0905.7 (P=1.45d), which consists of a 1.452(34)M_☉, 1.635(12)R_☉ primary and a 0.808(13)M_☉, 0.819(11)R_☉ secondary, is likely a pre-main sequence system. In all cases secondary eclipses are total.