Systematic Effects of Hydrogen and Helium Atmosphere Mismatch on Radius Inference in PSR~J0740+6620-like Synthetic NICER Data
Abstract
Constraints on neutron star radii provide insight into the properties of the cold, dense matter in their interiors. Previous studies using synthetic Neutron star Interior Composition Explorer (NICER) pulse waveform data have demonstrated that radius inferences derived therefrom are robust against several classes of modeling systematics. Here we explore the consequences of assuming the wrong atmospheric composition, using synthetic data based on the ∼ 2.1 M⊙ pulsar PSR~J0740+6620. We find that the assumption of a hydrogen atmosphere when the synthetic data assumed a helium atmosphere, or vice versa, produces little bias in the inferred radius at the spot-to-background ratio of the actual PSR~J0740+6620 data. However, when we increase the spot-to-background ratio by a factor of ∼20 while keeping the total number of counts fixed at the observed ∼ 5.5× 105, we find that composition mismatch can produce significantly biased radius estimates while remaining hidden inside a fit with statistically acceptable residuals. Even in these cases, the Bayesian evidence consistently identifies the correct atmospheric model. Our findings reinforce the importance of using the Bayesian evidence for model comparison and goodness-of-fit tests.
Versions
Related
- CNN-Based Inference of Gaseous Halo Properties from Synthetic X-ray and 21-cm HI Observations
- When the core ate the atmosphere
- Atmosphere mitigation in cosmic microwave background observations using multifrequency time-domain component separation
- Thermodynamic and structural properties of the thin atmosphere of a white dwarf
- Helium escaping from the atmosphere of a nearby rocky exoplanet orbiting in a habitable zone
BibTeX
@misc{holt2026systematic,
title = {{Systematic Effects of Hydrogen and Helium Atmosphere Mismatch on Radius Inference in PSR~J0740+6620-like Synthetic NICER Data}},
author = {Isiah M. Holt and M. Coleman Miller and Alexander J. Dittmann and Frederick K. Lamb},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.20795},
eprint = {2609.20795},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.20795},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Systematic Effects of Hydrogen and Helium Atmosphere Mismatch on Radius Inference in PSR~J0740+6620-like Synthetic NICER Data
AU - Isiah M. Holt
AU - M. Coleman Miller
AU - Alexander J. Dittmann
AU - Frederick K. Lamb
PY - 2026
DA - 2026/09/17
PB - arXiv
DO - 10.48550/arxiv.2609.20795
UR - https://arxiv.org/abs/2609.20795
AB - Constraints on neutron star radii provide insight into the properties of the cold, dense matter in their interiors. Previous studies using synthetic Neutron star Interior Composition Explorer (NICER) pulse waveform data have demonstrated that radius inferences derived therefrom are robust against several classes of modeling systematics. Here we explore the consequences of assuming the wrong atmospheric composition, using synthetic data based on the ∼ 2.1 M_⊙ pulsar PSR~J0740+6620. We find that the assumption of a hydrogen atmosphere when the synthetic data assumed a helium atmosphere, or vice versa, produces little bias in the inferred radius at the spot-to-background ratio of the actual PSR~J0740+6620 data. However, when we increase the spot-to-background ratio by a factor of ∼20 while keeping the total number of counts fixed at the observed ∼ 5.5× 10^5, we find that composition mismatch can produce significantly biased radius estimates while remaining hidden inside a fit with statistically acceptable residuals. Even in these cases, the Bayesian evidence consistently identifies the correct atmospheric model. Our findings reinforce the importance of using the Bayesian evidence for model comparison and goodness-of-fit tests.
ER -