Discovery of an unusual bright eclipsing binary with the longest known period: TYC 2505-672-1 / MASTER OT J095310.04+335352.8

TL;DR

This paper reports the discovery of an eclipsing binary star system with an unprecedented orbital period of 69.1 years, featuring a deep, gray eclipse and spectral evidence of a red giant eclipsed by a dusty disk around an unseen companion.

Contribution

It presents the first identification of a binary system with the longest known orbital period and detailed observational analysis of its unique eclipse characteristics.

Findings

Orbital period of 69.1 years, the longest known for an eclipsing binary.

Deep, symmetric eclipse lasting 3.5 years with over 4.5 magnitude depth.

Spectral evidence of a red giant and a hot source during eclipse.

Abstract

We report on the MASTER Global Robotic Net discovery of an eclipsing binary, MASTER OT J095310.04+335352.8, previously known as unremarkable star TYC 2505-672-1, which displays extreme orbital parameters. The orbital period P=69.1 yr is more than 2.5 times longer than that of epsilon-Aurigae, which is the previous record holder. The light curve is characterized by an extremely deep total eclipse with a depth of more than 4.5 mag, which is symmetrically shaped and has a total duration of 3.5 yrs. The eclipse is essentially gray. The spectra acquired with the Russian 6 m BTA telescope both at minimum and maximum light mainly correspond to an M0-1III--type red giant, but the spectra taken at the bottom of eclipse show small traces of a sufficiently hot source. The observed properties of this system can be better explained as the red giant eclipsed by a large cloud (the disk) of small particles surrounding the invisible secondary companion.