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Neutron star mass estimates from gamma-ray eclipses in spider millisecond pulsar binaries
C J Clark1,2,3, M Kerr4, E D Barr5
1Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Hannover, Germany.
Nature Astronomy
|April 25, 2023
Summary
Gamma-ray eclipses from spider systems provide new constraints on neutron star masses. This study found eclipses in seven systems, including PSR B1957+20, revealing a lighter pulsar mass than previously estimated.
Area of Science:
- Astronomy and Astrophysics
- Compact Binary Systems
- Neutron Star Physics
Background:
- Accurate neutron star mass measurements are crucial for understanding the equation of state of nuclear matter.
- Spider pulsars (black widows and redbacks) are compact binaries with millisecond pulsars and semi-degenerate companions.
- Optical spectroscopy provides inclination-dependent mass estimates, but is subject to systematic biases from heating models and variability.
Purpose of the Study:
- To search for gamma-ray eclipses in spider systems using Fermi Large Area Telescope data.
- To obtain robust, model-independent constraints on pulsar masses by analyzing gamma-ray eclipses.
- To refine mass estimates for neutron stars in compact binary systems.
Main Methods:
- Analyzed Fermi Large Area Telescope data for 49 spider systems.
- Searched for significant gamma-ray eclipses indicative of pulsar occultation.
- Used eclipse detection or exclusion to constrain binary inclination angles.
Main Results:
- Discovered significant gamma-ray eclipses in 7 out of 49 studied spider systems.
- The prototypical black widow pulsar, PSR B1957+20, exhibited a significant gamma-ray eclipse.
- The eclipse for PSR B1957+20 implies a pulsar mass of 1.81 ± 0.07 solar masses, lighter than optical estimates.
Conclusions:
- Gamma-ray eclipses offer a robust, model-independent method for constraining neutron star masses.
- The findings for PSR B1957+20 challenge previous mass estimates derived from optical light curve modeling.
- This technique can significantly improve our understanding of the equation of state for cold nuclear matter.
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