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The orbital parameters of gamma-ray binary PSR~J2032+4127

Yu-Feng Luo, Shan-Shan Weng, Qing-Zhong Liu, Ming-Yu Ge, Han-Long Peng, Shi-Qi Zhou, Shi-Jie Gao, Yu-Jia Zheng, Yan Zhang

Abstract

PSR~J2032+4127 is the only one of gamma-ray binary, that exhibits pulsations in gamma-ray. Previous research has indicated that the pulsar and the Be star MT91 213 orbit each other in a highly eccentric orbit with an extremely long period, with the pulsar reaching its periastron on November 13, 2017. Since its launch, the \fermi{} satellite has been monitoring this pulsar for 16 years, covering the 8 years before and the 8 years after the pulsar passed its periastron. Using these data, we present an analysis of pulse arrival times, and precisely determine the orbital parameters for the first time: the orbital period of $P_{\rm orb} \sim 52.3$ yr, the eccentricity of $e \sim 0.98$, the semimajor axis of $a$sin$i \sim 25.3$ AU, and the orbital inclination of $\sim$ 47.1$^\circ$ -- 55.1$^\circ$. We also reveal another small glitch occurred in 2021, MJD $\sim$ 59500.

The orbital parameters of gamma-ray binary PSR~J2032+4127

Abstract

PSR~J2032+4127 is the only one of gamma-ray binary, that exhibits pulsations in gamma-ray. Previous research has indicated that the pulsar and the Be star MT91 213 orbit each other in a highly eccentric orbit with an extremely long period, with the pulsar reaching its periastron on November 13, 2017. Since its launch, the \fermi{} satellite has been monitoring this pulsar for 16 years, covering the 8 years before and the 8 years after the pulsar passed its periastron. Using these data, we present an analysis of pulse arrival times, and precisely determine the orbital parameters for the first time: the orbital period of yr, the eccentricity of , the semimajor axis of sin AU, and the orbital inclination of 47.1 -- 55.1. We also reveal another small glitch occurred in 2021, MJD 59500.
Paper Structure (11 sections, 2 equations, 3 figures, 2 tables)

This paper contains 11 sections, 2 equations, 3 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Observation and timing analysis
  3. Data reduction
  4. Keplerian orbital parameter fitting
  5. Barycentric correction for binary systems
  6. TOAs of the binary system
  7. Results
  8. Orbital Period Determination with TEMPO2
  9. Glitch parameters
  10. Orbital inclination
  11. Summary

Figures (3)

  • Figure 1: The top panel illustrates the evolution of the neutron star's spin frequency $\nu$, with a reference value $\nu_0 = 6.9795$ Hz. Blue error bars denote the measured values, the red curve depicts the modeled spin frequency before orbital correction (derived from TEMPO2-fitted orbital and spin parameters), and black error bars show the intrinsic spin frequency after orbital demodulation. The middle panel shows the corresponding spin frequency derivative $\dot{\nu}$ ($\dot{\nu}_{0}$ = 5.6698 $\times$ 10$^{-13}$ Hz s$^{-1}$) as determined by TEMPO2. The bottom panel displays the fully coherent timing residuals (phase residuals) from the TEMPO2 orbital fit.
  • Figure 2: The NS rotation phase-time diagram after the barycenter correction of the binary star, with the Epoch MJD is 58070. The black dashed lines mark two glitches at MJD ∼55810.76 and 59500, respectively. The black solid line indicates the time of periastron passage. All phases are aligned with the first segment's phase subtracted.
  • Figure 3: The relationship between the orbital inclination and the Be star mass for a binary system with a NS primary of 1.4 M$_{\odot}$. The curve is derived from the mass function, showing the allowed combinations of inclination and Be star mass. The blue region indicates the uncertainty range.