Spin-down rate of the transitional millisecond pulsar PSR J1023+0038 in the optical band with Aqueye+

TL;DR

This paper reports the first optical timing solution and spin-down rate measurement of the transitional millisecond pulsar PSR J1023+0038, revealing differences compared to X-ray and radio observations, using high-resolution data from Aqueye+.

Contribution

First optical timing solution and spin-down rate measurement of PSR J1023+0038 using Aqueye+ data, providing new insights into its rotational behavior.

Findings

Optical spin-down rate measured as (-2.53 ± 0.04) × 10^{-15} Hz^2.

Optical spin-down rate is ~20% slower than X-ray measurements from 2013-2016.

Optical spin-down rate is ~5% faster than radio measurements during the rotation-powered state.

Abstract

We present a timing analysis of the transitional millisecond pulsar PSR J1023+0038 using observations taken between January 2018 and January 2020 with the high time resolution photon counter Aqueye+ mounted at the 1.82 m Copernicus telescope in Asiago. We report the first measurement of the timing solution and the frequency derivative of PSR J1023+0038 based entirely on optical data. The spin-down rate of the pulsar is $(-2.53 \pm 0.04) \times 10^{-15}$ Hz$^2$, which is $\sim$20% slower than that measured from the X-ray observations taken in 2013-2016 and $\sim$5% faster than that measured in the radio band during the rotation-powered state.