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 mag, Sp~=~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 $P_A$~=~$2^{d}.94$($e$=0.20) and pair "B" with the period $P_B$~=~$3^{d}.26$ ($e$=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 derived the mutual orbit of both pairs around the system barycenter with a period of 6.54 years and eccentricity $e$ = 0.71. We detected in pairs "A" and "B" the fast apsidal motion with the periods $U_A$~=~25.0 years and $U_B$~=~25.2 years, respectively. The orbit of each pair shows small nutation-like oscillations in periastron longitude. The age of the system estimated as 200 mln. years. The photometric parallax calculated from the found parameters coincides perfectly with the $GAIA~DR2$ $\pi$=$0.00407"\pm0.00006"$.