The optical companion to the intermediate mass millisecond pulsar J1439-5501 in the Galactic field

TL;DR

This paper identifies and characterizes the white dwarf companion to the pulsar J1439-5501, providing insights into its properties, system parameters, and age comparison, using deep optical imaging and theoretical models.

Contribution

First identification and detailed characterization of the white dwarf companion to pulsar J1439-5501 in the Galactic field.

Findings

White dwarf companion has mass between 1 and 1.3 solar masses.

System distance estimated to be less than 1200 parsecs.

Pulsar mass constrained to be less than approximately 2.2 solar masses.

Abstract

We present the identification of the companion star to the intermediate mass binary pulsar J1439-5501 obtained by means of ground-based deep images in the B, V and I bands, acquired with FORS2 mounted at the ESO-VLT. The companion is a massive white dwarf (WD) with B=23.57+-0.02, V=23.21+-0.01 and I=22.96+-0.01, located at only ~0.05" from the pulsar radio position. Comparing the WD location in the (B, B-V) and (V, V-I) Color-Magnitude diagrams with theoretical cooling sequences we derived a range of plausible combinations of companion masses (1<~Mcom<~1.3 Msun), distances (d<~1200 pc), radii (<~7.8 10^3 Rsun) and temperatures (T=31350^{+21500}_{-7400}). From the PSR mass function and the estimated mass range we also constrained the inclination angle i >~ 55 degrees and the pulsar mass (Mpsr <~2.2 Msun). The comparison between the WD cooling age and the spin down age suggests that the latter is overestimated by a factor of about ten.