A comparative study of binary synthesis modelling software for neutron star mass estimates

Binary star systems known as spiders consist of a millisecond pulsar ablating or accreting from its main sequence companion star. The pulsars in these systems are known for being quite massive and, as such, are useful in the effort to constrain the equation of state for nuclear matter. Accurate mass measurements of the neutron star in these systems are vital to the field, and are made using bespoke modelling software that simulate the system and generate model light curves. Through fitting these simulated curves to data, accurate estimates for the mass can be made. For years, various codes have been used independently but recently, a question about whether these codes will predict the same systemic parameters was raised. Here, we present the answer to this question in the context of the two most common spider modelling codes, Phoebe and Icarus, following the first ever comparison between them. We find that the codes behave quite similarly, as is expected, though there are some differences in how the surface gravity of the companion star is handled, which has some effects on the temperature predictions. We further explored whether the codes converge to the same conclusions when fitting data by considering the system LAMOST J112306.9+400736 using various constraints and comparing to a previous study by Yi et al. (2022) which used Phoebe. We find that both codes predict similar parameters, though there were some significant differences in the time required to fit a model and in how constrained a model needed to be. The ultimate choice between codes is personal to each researcher and neither choice will lead to less trustworthy results.

Grantor dc:publisher

University College Cork

Year dc:date.issued

2025

Author dc:creator

• Kennelly, Sorcha Riain

Advisor dc:contributor.advisor

• Kennedy, Mark

• Binary modelling codes
• Neutron star mass estimates
• Pulsars
• Spider binaries

Statement dc:rights

• © 2025, Sorcha Riain Kennelly.

Licence dc:rights.uri

• https://creativecommons.org/publicdomain/zero/1.0/

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10468/17965

OAI identifier oai:identifier

oai:cora.ucc.ie:10468/17965