Pulsar J0453+1559: A Double Neutron Star System with a Large Mass Asymmetry

Abstract: To understand the nature of supernovae and neutron star (NS) formation, as well as binary stellar evolution and their interactions, it is important to probe the distribution of NS masses. Until now, all double NS (DNS) systems have been measured to have a mass ratio close to unity (q $\geq$ 0.91). Here we report the measurement of the individual masses of the 4.07-day binary pulsar J0453+1559 from measurements of the rate of advance of periastron and Shapiro delay: The mass of the pulsar is 1.559(5) $M_{\odot}$ and that of its companion is 1.174(4) $M_{\odot}$; q = 0.75. If this companion is also a neutron star (NS), as indicated by the orbital eccentricity of the system (e=0.11), then its mass is the smallest precisely measured for any such object. The pulsar has a spin period of 45.7 ms and a spin derivative of 1.8616(7) x$10^-19$; from these we derive a characteristic age of ~ 4.1 x $10^9$ years and a magnetic field of ~ 2.9 x $10^9$ G,i.e, this pulsar was mildly recycled by accretion of matter from the progenitor of the companion star. This suggests that it was formed with (very approximately) its current mass. Thus NSs form with a wide range of masses, which is important for understanding their formation in supernovae. It is also important for the search for gravitational waves released during a NS-NS merger: it is now evident that we should not assume all DNS systems are symmetric.

Analysis of Pulsar J0453+1559: Mass Asymmetry in a Double Neutron Star System

The paper "Pulsar J0453+1559: A Double Neutron Star System with a Large Mass Asymmetry" discusses significant findings in the study of double neutron star (DNS) systems. The focus is on the discovery and analysis of the binary pulsar J0453+1559, which exhibits a notable mass asymmetry between its components. This paper contributes to understanding neutron star formation, binary stellar evolution, and the implications for gravitational wave detection.

Key Findings

The authors report precise measurements for the masses of the pulsar J0453+1559 and its companion. The pulsar has a mass of (M_{p} = 1.559 \pm 0.005 \, \Msun) and its companion (M_{c} = 1.174 \pm 0.004 \, \Msun). With a mass ratio (q = 0.75), J0453+1559 exhibits one of the largest known mass asymmetries in a DNS system. The companion's mass is particularly noteworthy as it represents the smallest precisely measured mass for any such object, suggesting a wide range of neutron star birth masses.

Observational Insights

The system was observed using the Arecibo radio telescope, leveraging the PUPPI backend to gather data over a 2.5-year period. Key techniques used include measuring the rate of advance of periastron and Shapiro delay to determine the mass of the component stars. The precise timing solution for PSR J0453+1559 reveals a spin period of 45.7 ms and a spin-down rate, leading to a characteristic age of approximately 4.1 billion years. This points towards a mildly recycled pulsar, accreting matter from the progenitor of the companion star.

Implications for Neutron Star Formation

The findings challenge the previously held notion that neutron stars in DNS systems have a narrow range of birth masses. The mass of J0453+1559, in particular, demonstrates that neutron stars can be born with significantly varying masses, which has profound implications for models of supernova events and neutron star formation. This discovery necessitates a reevaluation of the mechanisms by which neutron stars inherit mass during their formation.

Significance for Gravitational Wave Searches

The mass asymmetry in J0453+1559, coupled with its orbital characteristics, has significant implications for gravitational wave detection. It highlights the need for revised templates in gravitational wave searches that account for asymmetric DNS systems. The study's results encourage the consideration of asymmetric systems in simulations of DNS mergers, potentially impacting predictions of gravitational wave emissions and the resultant astrophysical environments.

Theoretical and Practical Perspectives

From a theoretical standpoint, this research contributes to our understanding of asymmetric DNS systems and the distribution of neutron star masses. Practically, it underscores developments in observational techniques for binary systems using radio telescopes. Additionally, the study suggests future directions for observing systems with similar mass asymmetries, potentially expanding the scope of gravitational wave detection methodologies.

In summary, the paper presents a meticulous analysis of a unique DNS system, expanding our comprehension of neutron star characteristics and informing future astrophysical inquiries and gravitational wave research.