Optical detection of the black widow binary PSR J2052+1219

TL;DR

This study uses optical photometry to identify and analyze the companion star of the black widow pulsar PSR J2052+1219, estimating system parameters and comparing it with other similar systems.

Contribution

First optical detection and detailed modeling of the companion star of PSR J2052+1219, providing independent distance measurement and system characterization.

Findings

Optical counterpart identified with orbital period matching radio data.

Estimated distance of 3.94 kpc consistent with dispersion measure.

Companion star nearly fills Roche lobe with a 3000 K temperature difference.

Abstract

We present optical time-resolved multi-band photometry of the black widow binary millisecond pulsar J2052+1219 using direct-imaging observations with the 2.1m telescope of Observatorio Astronomico Nacional San Pedro Martir, Mexico (OAN-SPM). The observations revealed a variable optical source whose position and periodicity P = 2.752h coincide with the pulsar coordinates and the orbital period obtained from radio timing. This allowed us to identify it with the binary companion of the pulsar. We reproduce light curves of the source modelling the companion heating by the pulsar and accounting for the system parameters obtained from the radio data. As a result, we independently estimate the distance to the system of 3.94(16) kpc, which agrees with the dispersion measure distance. The companion star size is 0.12-0.15 Rsun, close to filling its Roche lobe. It has a surface temperature difference of about 3000 K between the side facing the pulsar and the back side. We summarise characteristics of all black widow systems studied in the optical and compare them with the PSR J2052+1219 parameters derived from our observations.