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Spider pulsars continue to provide promising candidates for neutron star mass measurements. Here we present the discovery of PSR J1910−5320, a new millisecond pulsar discovered in a MeerKAT observation of an unidentified Fermi-LAT gamma-ray source. This pulsar is coincident with a recently identified candidate redback binary, independently discovered through its periodic optical flux and radial velocity. New multi-color optical light curves obtained with ULTRACAM/NTT in combination with MeerKAT timing and updated SOAR/Goodman spectroscopic radial velocity measurements allow a mass constraint for PSR J1910−5320. Icarus optical light curve modelling, with streamlined radial velocity fitting, constrains the orbital inclination and companion velocity, unlocking the binary mass function given the precise radio ephemeris. Our modelling aims to unite the photometric and spectroscopic measurements available by fitting each simultaneously to the same underlying physical model, ensuring self-consistency. This targets centre-of-light radial velocity corrections necessitated by the irradiation endemic to spider systems. Depending on the gravity darkening prescription used, we find a moderate neutron star mass of either 1.6 ± 0.2 or 1.4 ± 0.2 M⊙. The companion mass of either 0.45 ± 0.04 or $$0.43^{+0.04}_{-0.03}$$ M⊙ also further confirms PSR J1910−5320 as an irradiated redback spider pulsar.
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This content will become publicly available on December 22, 2026
Optical study of TRAPUM pulsars and modelling of the redbacks: PSR J1036−4353 and PSR J1803−6707
ABSTRACT The Transients and Pulsars with MeerKAT (TRAPUM) project discovered eight binary millisecond pulsars in its first shallow L-band survey of unidentified Fermi $$\gamma$$-ray sources using the MeerKAT radio telescope. We conducted follow-up observations using ULTRACAM on the New Technology Telescope at the La Silla Observatory to search for the optical counterpart to the pulsar companions. We found two redback companions, in PSRs J1803–6707 and J1036–4353, and provided upper limits for the other pulsar binaries. We used the Icarus code to fit the redback’s light curves using various irradiation models. The asymmetric double-peak light curves of PSR J1036–4353 are best fit with diffusion and convection models. Comparing the two prescriptions of irradiation and gravity darkening, models with post-irradiation gravity darkening provide superior fits (particularly for lower gravity-darkening exponents), suggesting that the irradiation energy is deposited deep in the stellar photosphere. PSR J1803–6707, on the other hand, displayed variability in the amplitude of its irradiation-dominated light curves over a time-scale of a few months. This effect can be modelled only if the companion’s filling, irradiation temperature, and convection coefficients are allowed to vary over time. Had the star been closer to filling its Roche lobe, like in the cases of the known transitional millisecond pulsars J1023+0038 and J1227–4853, this 4.1 per cent variation in the volume-averaged filling of the star would have caused it to experience a state change to form an active accretion disc.
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- Award ID(s):
- 2205631
- PAR ID:
- 10703063
- Publisher / Repository:
- OUP
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 545
- Issue:
- 3
- ISSN:
- 0035-8711
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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