Recent studies have provided precise measurements of the nearest millisecond pulsar, PSR J0437-4715, revealing its radius to be 11.4 kilometers and its mass 1.4 times that of the Sun.
This research, led by a team from the University of Amsterdam, provides deeper insights into the composition and magnetic field of this neutron star.
Precise measurements and innovative techniques
PSR J0437-4715 is a rotating neutron star located about 510 light-years from Earth in the constellation Pictor. It rotates 174 times per second and has a white dwarf companion. The pulsar fires a beam of radio waves and X-rays toward Earth every 5.75 milliseconds, making it the closest and brightest millisecond pulsar known.
To achieve these precise measurements, the team used data from NICER X-ray telescope on board International Space Station (ISS) and applied pulse profile modeling, which involves complex statistical models processed on the Dutch national supercomputer Snellius.
Researchers joined X-ray data with mass measurements taken by Daniel Reardon and colleagues at the Parkes Pulsar Timing Array. This combination allowed them to calculate the ray of the star and draft it temperature distribution of its magnetic poles. “Before, we hoped to be able to calculate the radius precisely. And it would be nice if we could show that the hot magnetic poles are not directly opposite each other on the stellar surface. And we just managed to make them both,” said principal investigator Devarshi Choudhury.
The use of NICER data was crucial for this study, as it provided the high-precision timing needed to analyze the pulse profiles of the pulsar. The data revealed that the pulsar hotspots, regions where X-rays are emitted due to the intense magnetic field, they are not located symmetrically. This asymmetry offered new challenges and insights in the modeling of interior of the neutron star.
Insights into neutron star composition and behavior
New measurements of PSR J0437-4715 indicate a “softer equation of state” than previously thought. This suggests that the maximum mass of neutron stars should be lower than some theories predict, matching observations of gravitational waves. Anna Watts, a neutron star expert at the University of Amsterdam, explained, “And that, in turn, fits well with what the gravitational wave observations seem to suggest.”
These findings suggest that matter inside neutron stars it is less dense and more compressible than previously believed. This affects our understanding of the properties of ultra-dense matter, which cannot be recreated in laboratories on Earth. Measurement of neutron star beamcombined with its mass, helps physicists constrain the equation of state that describes how matter behaves at the extreme densities found in neutron stars.
The research also found that the hot magnetic poles of PSR J0437-4715 are not directly opposite each other, providing new insights into the star’s magnetic field and temperature distribution. This anomaly in the alignment of the magnetic poles may have implications for our understanding of magnetic field dynamics and the internal structure of neutron stars. Mapping the temperature distribution at the pulsar surface further adds to our understanding of the thermal processes occurring within these dense objects.
Implications for understanding neutron star physics
This study is part of a series of works on millisecond pulsars, contributing to a wider understanding of these fascinating objects. Future research will continue to explore the equation of state and mass relations of neutron stars, with additional papers focusing on other heavy pulsars and their characteristics.
The findings from this research have important implications for our understanding of neutron stars and the extreme physics that govern their behavior. By refining our knowledge of the mass and radius of these stars, scientists can better understand the limits of neutron star stability and the fundamental properties of matter under extreme conditions. This research also supports the development of more accurate models for neutron star behavior, which are essential for interpreting observations from gravitational wave detectors such as LIGO and Virgo.
Accurate measurements of PSR J0437-4715 provided by the University of Amsterdam team marks an important advance in neutron star research. These findings not only deepen our understanding of this particular pulsar, but also contribute to the broader field of astrophysics, increasing our knowledge of the universe’s most extreme objects. Continued efforts to study neutron stars with advanced instruments such as BETTER and supercomputers underscore the importance of multidisciplinary approaches in unraveling the mysteries of the cosmos.