Exploring the Effect of Periastron Advance in Small-Eccentricity Binary Pulsars

TL;DR

This paper introduces the ELL1k timing model to measure periastron advance in small-eccentricity binary pulsars, enabling better constraints on pulsar companion properties without disrupting existing pulsar timing array efforts.

Contribution

The paper develops and implements the ELL1k model in TEMPO2, allowing detection of secular periastron advance in small-eccentricity binaries, which was not feasible with previous models.

Findings

Simulations show potential to measure periastron advance in specific pulsars.

The ELL1k model can constrain the apsidal motion constant of pulsar companions.

The model integrates seamlessly with ongoing Pulsar Timing Array campaigns.

Abstract

Short-orbital period small-eccentricity binary pulsars can, in principle, experience substantial advance of periastron. We explore the possibility of measuring this effect by implementing a timing model, ELL1k, in the popular TEMPO2 pulsar timing package. True secular variations in the Laplace-Lagrange parameters, present in our ELL1k model, can lead to measurable timing residuals while pursuing decade-long timing campaigns using the existing ELL1 timing model of Lange et al. (2001), especially for binaries exhibiting significant periastron advance. We also list the main differences between our approach and various implementations of the ELL1 model present in both TEMPO and TEMPO2 packages. Detailed TEMPO2 simulations suggest the possibility of constraining the apsidal motion constant of pulsar companions in certain observed binary pulsars with minuscule eccentricities such as PSR J1719-1438. Fortunately, the ELL1k timing model does not pose any challenges to the on-going Pulsar Timing Array campaigns that routinely employ the ELL1 timing model. Detailed TEMPO2 simulations suggest the possibility of constraining the apsidal motion constant of pulsar companions in certain observed binary pulsars with minuscule eccentricities such as PSR J1719-1438. Fortunately, the ELL1k timing model does not pose any challenges to the on-going Pulsar Timing Array campaigns that routinely employ the ELL1 timing model.