Optical identification of the binary companion to the millisecond PSR J2302+4442 with the Gran Telescopio Canarias

TL;DR

This study successfully identified the optical companion to the millisecond pulsar J2302+4442 using the Gran Telescopio Canarias, providing insights into its nature, mass, temperature, and the system's inclination.

Contribution

First optical detection and characterization of the binary companion to PSR J2302+4442, combining optical and radio data to constrain system parameters.

Findings

Companion is likely a He or CO-core white dwarf.

Estimated companion mass is approximately 0.52 solar masses.

System inclination angle is about 73 degrees.

Abstract

We report detection of the binary companion to the millisecond pulsar J2302+4442 based on the deep observations performed with the Gran Telescopio Canarias. The observations revealed an optical source with $r'$ = 23.33$\pm$0.02 and $i'$=23.08$\pm$0.02, whose position coincides with the pulsar radio position. By comparing the source colour and magnitudes with the white dwarf cooling predictions, we found that it likely represents a He or CO-core white dwarf and estimated its mass of 0.52$^{+0.25}_{-0.19}$ M$_{\odot}$ and effective temperature of 6300$^{+1000}_{-800}$ K. Combining our results with the radio timing measurements, we set constraints on the binary system inclination angle $i=73^{+6}_{-5}$ degrees and the pulsar mass $m_p=3.1^{+2.7}_{-2.0}$ M$_{\odot}$.