A NICER view of the millisecond pulsar PSR J2124−3358: evidence for a helium atmosphere
Abstract
Pulse profile modeling has proven to be a powerful technique for determining the mass and radius of neutron stars. To date, this method has been applied to a handful of millisecond pulsars observed by the Neutron Star Interior Composition Explorer (NICER). However, analyses of more millisecond pulsars are necessary to determine tight constraints on the equation of state of superdense matter. In this study, we present an analysis of the isolated, rotation-powered millisecond pulsar PSR J2124−3358 using the X-ray Pulse Simulation and Inference (X-PSI) package, a publicly available state-of-the-art code for neutron-star relativistic ray tracing and Bayesian parameter inference. We use NICER and Chandra observations of this pulsar, exploring different neutron star atmospheric compositions and different configurations of the hot polar caps responsible for the pulsed X-ray emission. Our analyses favor a helium atmospheric composition, plausibly originating from accretion and subsequent evaporation of a former hydrogen-depleted binary companion. For this composition, and given the faint nature of the source and the low signal-to-noise of the data sets, we obtain broad posterior distributions yielding a mass M = 1.8±0.5 M⊙ and an equatorial radius Req = 11.7+2.6−3.0 km (medians and 68% credible intervals), and infer a configuration consisting of two slightly non-antipodal hot spots. By contrast, when using a hydrogen atmosphere model, the mass and radius decrease by ∼ 0.5 M⊙ and ∼ 1 km, respectively. Future multiwavelength studies, particularly those incorporating radio and gamma-ray pulse-emission, may provide tighter constraints on the geometry and physical properties of this source.
Related
- A NICER view of PSR J1614−2230: a massive and compact millisecond pulsar
- Systematic Effects of Hydrogen and Helium Atmosphere Mismatch on Radius Inference in PSR J0740+6620–like Synthetic NICER Data
- Systematic Effects of Hydrogen and Helium Atmosphere Mismatch on Radius Inference in PSR~J0740+6620-like Synthetic NICER Data
- Evidence of Orbital Evolution of Gigahertz-peaked Spectra in a Binary Millisecond Pulsar
- Evidence of Orbital Evolution of Gigahertz-Peaked Spectra in Binary Millisecond Pulsar
BibTeX
@misc{gonzalezcaniulef2026nicer,
title = {{A NICER view of the millisecond pulsar PSR J2124$-$3358: evidence for a helium atmosphere}},
author = {Denis González-Caniulef and Sebastien Guillot and Pierre Stammler and Lucien Mauviard and Christine Kazantsev and Anna L Watts and Devarshi Choudhury and Bas Dorsman and Mariska Hoogkamer and Daniela Huppenkothen and Yves Kini and Tuomo Salmi and Lucas Guillemot and Ismaël Cognard and Gilles Theureau},
howpublished = {HAL},
year = {2026},
month = sep,
eprint = {2607.03721},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05734281v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A NICER view of the millisecond pulsar PSR J2124−3358: evidence for a helium atmosphere
AU - Denis González-Caniulef
AU - Sebastien Guillot
AU - Pierre Stammler
AU - Lucien Mauviard
AU - Christine Kazantsev
AU - Anna L Watts
AU - Devarshi Choudhury
AU - Bas Dorsman
AU - Mariska Hoogkamer
AU - Daniela Huppenkothen
AU - Yves Kini
AU - Tuomo Salmi
AU - Lucas Guillemot
AU - Ismaël Cognard
AU - Gilles Theureau
PY - 2026
DA - 2026/09/02
PB - HAL
UR - https://hal.science/hal-05734281v1
AB - Pulse profile modeling has proven to be a powerful technique for determining the mass and radius of neutron stars. To date, this method has been applied to a handful of millisecond pulsars observed by the Neutron Star Interior Composition Explorer (NICER). However, analyses of more millisecond pulsars are necessary to determine tight constraints on the equation of state of superdense matter. In this study, we present an analysis of the isolated, rotation-powered millisecond pulsar PSR J2124−3358 using the X-ray Pulse Simulation and Inference (X-PSI) package, a publicly available state-of-the-art code for neutron-star relativistic ray tracing and Bayesian parameter inference. We use NICER and Chandra observations of this pulsar, exploring different neutron star atmospheric compositions and different configurations of the hot polar caps responsible for the pulsed X-ray emission. Our analyses favor a helium atmospheric composition, plausibly originating from accretion and subsequent evaporation of a former hydrogen-depleted binary companion. For this composition, and given the faint nature of the source and the low signal-to-noise of the data sets, we obtain broad posterior distributions yielding a mass M = 1.8±0.5 M_⊙ and an equatorial radius R_eq = 11.7^+2.6_−3.0 km (medians and 68% credible intervals), and infer a configuration consisting of two slightly non-antipodal hot spots. By contrast, when using a hydrogen atmosphere model, the mass and radius decrease by ∼ 0.5 M_⊙ and ∼ 1 km, respectively. Future multiwavelength studies, particularly those incorporating radio and gamma-ray pulse-emission, may provide tighter constraints on the geometry and physical properties of this source.
ER -