PSR J1618-3921: a recycled pulsar in an eccentric orbit

TL;DR

This paper provides a detailed timing analysis of the recycled pulsar PSR J1618-3921, confirming its unusual orbital eccentricity and discussing possible formation scenarios based on multi-year observations.

Contribution

It offers the first precise measurement of the pulsar's spin, astrometric, and orbital parameters, clarifying its eccentric orbit and contributing to understanding recycled pulsar formation.

Findings

Confirmed the pulsar's large orbital eccentricity (~0.027)

Provided a precise timing-based ephemeris for PSR J1618-3921

Discussed formation hypotheses for eccentric recycled pulsars

Abstract

PSR~J1618$-$3921 is an $11.99$-ms pulsar in a $22.7$-d orbit around a likely low-mass He white dwarf companion, discovered in a survey of the intermediate Galactic latitudes at 1400 MHz conducted with the Parkes radio telescope in the late 1990s. Although PSR~J1618$-$3921 was discovered more than 15 years ago, only limited information has been published about this pulsar which has a surprisingly large orbital eccentricity ($e \simeq 0.027$), considering its high spin frequency and likely small companion mass. The focus of this work is a precise measurement of the spin, astrometric and orbital characteristics of PSR J1618$-$3921. This was done with timing observations made at the Nan\c{c}ay Radio Telescope, from 2009 to 2017. We analyzed the timing data recorded at the Nan\c{c}ay Radio Telescope over several years to characterize the properties of PSR~J1618$-$3921. A rotation ephemeris for this pulsar was obtained by analyzing the times of arrival of the radio pulses at the telescope. We confirm the unusual eccentricity of PSR~J1618$-$3921 and discuss several hypotheses regarding its formation, in the context of other discoveries of recycled pulsars in eccentric orbits.