Transformation of a Star into a Planet in a Millisecond Pulsar Binary

TL;DR

This paper investigates the origin of solitary millisecond pulsars by analyzing PSR J1719-1438, revealing it is in a tight binary with a low-mass white dwarf companion, suggesting a transformation process involving accretion and binary evolution.

Contribution

It presents evidence that some solitary millisecond pulsars originate from ultra-compact binary systems where the companion was nearly destroyed.

Findings

PSR J1719-1438 is in a 2.2-hour binary system.

The companion has a mass near that of Jupiter.

The companion's density suggests it is an ultra-low mass white dwarf.

Abstract

Millisecond pulsars are thought to be neutron stars that have been spun-up by accretion of matter from a binary companion. Although most are in binary systems, some 30% are solitary, and their origin is therefore mysterious. PSR J1719-1438, a 5.7 ms pulsar, was detected in a recent survey with the Parkes 64m radio telescope. We show that it is in a binary system with an orbital period of 2.2 h. Its companion's mass is near that of Jupiter, but its minimum density of 23 g cm$^{-3}$ suggests that it may be an ultra-low mass carbon white dwarf. This system may thus have once been an Ultra Compact Low-Mass X-ray Binary, where the companion narrowly avoided complete destruction.