A 62-minute orbital period black widow binary in a wide hierarchical triple

TL;DR

This paper reports the discovery of a unique black widow binary system with a 62-minute orbital period in a wide hierarchical triple, challenging existing models and providing insights into neutron star physics and binary evolution.

Contribution

It presents the first observation of a wide hierarchical triple black widow system with an extremely short orbital period, expanding understanding of binary evolution and neutron star formation.

Findings

Orbital period of 62 minutes, shorter than the 80-minute minimum for hydrogen-rich systems.

Presence of a low metallicity cool subdwarf tertiary companion.

System's Galactic halo orbit suggests unique formation and evolutionary history.

Abstract

Over a dozen millisecond pulsars are ablating low-mass companions in close binary systems. In the original "black widow", the 8-hour orbital period eclipsing pulsar PSR J1959+2048 (PSR B1957+20), high energy emission originating from the pulsar is irradiating and may eventually destroy a low-mass companion. These systems are not only physical laboratories that reveal the dramatic result of exposing a close companion star to the relativistic energy output of a pulsar, but are also believed to harbour some of the most massive neutron stars, allowing for robust tests of the neutron star equation of state. Here, we report observations of ZTF J1406+1222, a wide hierarchical triple hosting a 62-minute orbital period black widow candidate whose optical flux varies by a factor of more than 10. ZTF J1406+1222 pushes the boundaries of evolutionary models, falling below the 80 minute minimum orbital period of hydrogen-rich systems. The wide tertiary companion is a rare low metallicity cool subdwarf star, and the system has a Galactic halo orbit consistent with passing near the Galactic center, making it a probe of formation channels, neutron star kick physics, and binary evolution.