BU CMi as a quadruple doubly eclipsing system

TL;DR

This paper reports the discovery that BU CMi, previously known as a spectroscopic binary, is actually a quadruple system with two eclipsing binaries orbiting each other, providing detailed orbital and physical parameters.

Contribution

The study reveals BU CMi as a quadruple doubly eclipsing system with detailed orbital dynamics and physical characteristics, a novel classification for this star.

Findings

BU CMi is a 2+2 quadruple system with two detached eclipsing binaries.

Both binaries have nearly equal component sizes, masses, and temperatures.

The system's mutual orbit has a period of 6.54 years with high eccentricity.

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 $GAIA~DR2$ $\pi$=$0.00407"\pm0.00006"$.