Sharpening the Mass Measurement of PSR J1048+2339 via High-Cadence Photometry
Abstract
Neutron stars are among the densest objects in the universe, and the mass measurements are crucial to the understanding of their equation of state. Pulsars in tight binaries can be weighed dynamically, but accurate mass estimates are often hampered by uncertainties in orbital inclinations. In this paper, we report on multi-epoch optical monitoring of the pulsar binary, PSR J1048+2339, using the 0.5-m RIFT telescope at Lulin Observatory. Our observations reveal frequent optical flares with eclipses caused by the companion. Using the eclipse duration with archival photometric data and orbital ephemeris in the literature, we constrain the inclination to 78.0+/-1.0 degrees and the pulsar mass to 1.79 (+0.09, -0.08) solar masses. This measurement is among the most precise for any redback system to date, demonstrating a novel way to improve the pulsar mass measures with small aperture optical telescopes. Furthermore, the optical eclipse duration is significantly shorter than that measured in M/GeV gamma-rays, possibly suggesting that a fraction of the eclipsed gamma-ray emission originates from the apex of the intrabinary shock. Based on these constraints, we estimate the magnetic field strength of the companion to be 30-170 G. This is consistent with the high field strength implied by the X-ray orbital modulation observed.
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BibTeX
@misc{li2026sharpening,
title = {{Sharpening the Mass Measurement of PSR J1048+2339 via High-Cadence Photometry}},
author = {Kwan-Lok Li and Ka-Yui Au and Lupin C. C. Lin and C. Y. Hui and Albert K. H. Kong and Jumpei Takata},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.08456},
eprint = {2609.08456},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.08456},
}
RIS
TY - UNPB
TI - Sharpening the Mass Measurement of PSR J1048+2339 via High-Cadence Photometry
AU - Kwan-Lok Li
AU - Ka-Yui Au
AU - Lupin C. C. Lin
AU - C. Y. Hui
AU - Albert K. H. Kong
AU - Jumpei Takata
PY - 2026
DA - 2026/09/08
PB - arXiv
DO - 10.48550/arxiv.2609.08456
UR - https://arxiv.org/abs/2609.08456
AB - Neutron stars are among the densest objects in the universe, and the mass measurements are crucial to the understanding of their equation of state. Pulsars in tight binaries can be weighed dynamically, but accurate mass estimates are often hampered by uncertainties in orbital inclinations. In this paper, we report on multi-epoch optical monitoring of the pulsar binary, PSR J1048+2339, using the 0.5-m RIFT telescope at Lulin Observatory. Our observations reveal frequent optical flares with eclipses caused by the companion. Using the eclipse duration with archival photometric data and orbital ephemeris in the literature, we constrain the inclination to 78.0+/-1.0 degrees and the pulsar mass to 1.79 (+0.09, -0.08) solar masses. This measurement is among the most precise for any redback system to date, demonstrating a novel way to improve the pulsar mass measures with small aperture optical telescopes. Furthermore, the optical eclipse duration is significantly shorter than that measured in M/GeV gamma-rays, possibly suggesting that a fraction of the eclipsed gamma-ray emission originates from the apex of the intrabinary shock. Based on these constraints, we estimate the magnetic field strength of the companion to be 30-170 G. This is consistent with the high field strength implied by the X-ray orbital modulation observed.
ER -