The White Dwarf Companion of a 2 M_sun Neutron Star

TL;DR

This paper reports the discovery and analysis of a white dwarf companion to a massive millisecond pulsar, challenging existing models of pulsar recycling and providing insights into the system's evolution.

Contribution

It presents the first optical identification of the companion to PSR J1614-2230 and analyzes its properties to challenge simple pulsar recycling models.

Findings

The companion is a 2.2 Gyr old He-CO white dwarf.

The pulsar was born with a spin close to its current value.

Mass and age measurements challenge the standard recycling model.

Abstract

We report the optical discovery of the companion to the 2 M_sun millisecond pulsar PSR J1614-2230. The optical colors show that the 0.5 M_sun companion is a 2.2 Gyr old He-CO white dwarf. We infer that $\dot{M}$ during the accretion phase is <10^{-2}\dot{M}_{edd}. We show that the pulsar was born with a spin close to its current value, well below the rebirth line. The spin-down parameters, the mass of the pulsar, and the age of the system challenge the simple recycling model for the formation of millisecond pulsars.