The loudest stellar heartbeat: characterizing the most extreme amplitude heartbeat star system

We characterize the extreme heartbeat star system MACHO 80.7443.1718 in the Large Magellanic Cloud using Transiting Exoplanet Survey Satellite (TESS) photometry and spectroscopic observations from the Magellan Inamori Kyocera Echelle (MIKE) and SOAR Goodman spectographs. MACHO 80.7443.1718 was first identified as a heartbeat star system in the All-Sky Automated Survey for SuperNovae (ASAS-SN) with P-orb = 32.836 +/- 0.008 d. MACHO 80.7443.1718 is a young (similar to 6 Myr), massive binary, composed of a B0 Iae supergiant with M-1 similar or equal to 35M(circle dot) and an O9.5V secondary with M-2 similar or equal to 16M(circle dot) on an eccentric (e = 0.51 +/- 0.03) orbit. In addition to having the largest variability amplitude amongst all known heartbeats stars, MACHO 80.7443.1718 is also one of the most massive heartbeat stars yet discovered. The B[e] supergiant has Balmer emission lines and permitted/forbidden metallic emission lines associated with a circumstellar disc. The disc rapidly dissipates at periastron that could indicate mass transfer to the secondary, but re-emerges immediately following periastron passage. MACHO 80.7443.1718 also shows tidally excited oscillations at the N = 25 and N = 41 orbital harmonics and has a rotational period of 4.4 d.

Automated summary

MACHO 80.7443.1718 is a young, massive binary star system with a significant variability amplitude, one of the most massive heartbeat stars known. It exhibits Balmer emission lines and permitted/forbidden metallic emission lines associated with a circumstellar disc.