Optical identification of the millisecond pulsar J0621+2514

TL;DR

This study identifies a likely white dwarf companion to the millisecond pulsar J0621+2514 using survey data, providing insights into its properties and implications for pulsar age estimates.

Contribution

First optical identification of the companion to pulsar J0621+2514, characterizing its type, temperature, and age, and discussing implications for pulsar age estimation.

Findings

Companion is likely a He-core white dwarf with ~10,000 K temperature.

White dwarf's cooling age is less than 0.5 Gyr, younger than pulsar characteristic age.

The pulsar's age may be overestimated or explained by white dwarf properties.

Abstract

Using the SDSS and Pan-STARRS1 survey data, we found a likely companion of the recently discovered binary $\gamma$-ray radio-loud millisecond pulsar J0621+2514. Its visual brightness is about 22 mag. The broad band magnitudes and colours suggest that this is a white dwarf. Comparing the data with various white dwarfs evolutionary tracks, we found that it likely belongs to a class of He-core white dwarfs with a temperature of about 10 000 K and a mass of $\lesssim 0.5$M$_\odot$. For a thin hydrogen envelope of the white dwarf its cooling age is $\lesssim0.5$ Gyr which is smaller than the pulsar characteristic age of 1.8 Gyr. This may indicate that the pulsar age is overestimated. Otherwise, this may be explained by the presence of a thick hydrogen envelope or a low metallicity of the white dwarf progenitor.