BU CMi as a Quadruple Doubly Eclipsing System

Abstract

We found that the known spectroscopic binary and variable BU CMi = HD65241 (V = 6.4{-} {{6.7}^{{text{m}}}}, A0 V) is a quadruple doubly eclipsing 2+2 system. Both eclipsing binaries are detached systems moving in an eccentric orbits: pair “A” with the period {{P}_{{text{A}}}} = {{2}^{{text{d}}}}.94 (e = 0.20) and pair “B” with the period {{P}_{{text{B}}}} = {{3}^{{text{d}}}}.26 (e = 0.22). All four components have nearly equal sizes, temperatures and masses in the range M = 3.1{-} 3.4,{{M}_{ odot }}, and A0 spectra. We found the mutual orbit of both pairs around the system barycenter with a period of 6.6 years and eccentricity e = 0.7. We detected in pairs “A” and “B” the fast apsidal motion with the periods {{U}_{{text{A}}}} = 25.4 years and UB = 26.3 years, respectively. The orbit of each pair shows small nutation like oscillations in periastron longitude. The system is young and it seems that its components does not yet reached the Zero Age Main Sequence (ZAMS). The photometric parallax calculated from the found parameters coincides perfectly with the GAIA DR2 pi =0.00407'' pm 0.00006'' .