Discovery and timing of pulsar J2016$+$3711 in supernova remnant CTB 87 with FAST (2402.00578v1)

Abstract: We report on our discovery of the radio pulsar, PSR J2016$+$3711, in supernova remnant (SNR) CTB 87, with a $\sim10.8\sigma$ significance of pulses, which confirms the compact nature of the X-ray point source in CTB 87. It is the first pulsar discovered in SNRs using Five-hundred-meter Aperture Spherical radio Telescope (FAST). Its integrated radio pulse profile can be well described by a single component, with a width at 50% of the peak flux density of about 28.1$^\circ$ and an effective width of about 32.2$^\circ$. The mean flux density at 1.25 GHz is estimated to be about 15.5$\mu$Jy. Combined with the non-detection of the radio pulse at lower frequencies, the radio spectral index of the pulsar is constrained to be $\lesssim 2.3$. We also present the timing solution based on 28 follow-up FAST observations. Our results reveal a period of 50.81 ms, period derivative of $7.2\times 10^{-14}$ s s$^{-1}$, and dispersion measure of 428 pc cm$^{-3}$. The strength of the equatorial surface magnetic dipole magnetic field is inferred to be about $1.9\times10^{12}$ G. Using the ephemeris obtained from the radio observations, we searched Fermi-LAT data for gamma-ray pulsations but detected no pulsed signal. We also searched for radio pulses with FAST toward the X-ray counterpart of the gamma-ray binary HESS J1832$-$093 proximate to SNR G22.7$-$00.2 but found no signal.

• The paper reports the discovery of PSR J2016+3711, marking the first identification of an SNR-associated pulsar using FAST's sensitive radio observations.
• The timing analysis from 28 follow-up observations yielded a precise 50.81-ms pulse period and a period derivative of 7.2×10⁻¹⁴ s/s.
• The study underscores FAST's capability in detecting faint radio signals (~15.5 μJy at 1.25 GHz) and highlights implications for multi-wavelength pulsar research.

Discovery and Timing of PSR J2016+3711 in the Supernova Remnant CTB 87 using FAST

The paper "Discovery and Timing of Pulsar J2016+3711 in Supernova Remnant CTB with FAST" reports the discovery of a new pulsar, PSR J2016+3711, within the supernova remnant (SNR) CTB 87, utilizing the Five-hundred-meter Aperture Spherical radio Telescope (FAST). This discovery marks the first instance of employing FAST to identify a pulsar associated with supernova remnants (SNRs), underscoring the telescope's high sensitivity in detecting faint radio sources.

Discovery Process

The detection of PSR J2016+3711, located in SNR CTB 87, is characterized by a significant radio pulse signal with a $\sim 10.8\sigma$ level. The pulsar's discovery provides confirmation of the compact nature of the X-ray point source in the remnant. FAST's unprecedented sensitivity enabled the identification of this faint pulsar with an estimated mean flux density of approximately 15.5 $\mu$Jy at 1.25 GHz.

Observational Detail and Findings

The pulsar exhibits an integrated radio pulse profile best described by a single component with a width at 50% of the peak flux density approximately $28.1^\circ$, and an effective width about $32.2^\circ$. The timing solution derived from 28 follow-up observations reveals a pulse period of 50.81 ms and a period derivative of $7.2 \times 10^{-14}$ s/s, with a dispersion measure (DM) of 428 pc cm$^{-3}$. The strength of the inferred equatorial surface magnetic dipole is around 1.9 × 10^12 G.

Implications of the Radio and Gamma-Ray Analysis

Although gamma-ray pulsation was sought in conjunction with Fermi-LAT data for PSR J2016+3711, none was detected. This result prompts considerations of the pulsar's emission mechanisms and orientation, suggesting possible misalignments or obscured line-of-sight emissions that prevent gamma-ray detection.

Contribution to Astrophysical Research

This work significantly contributes to the understanding of the relationship between pulsars and SNRs. The different nature and orientation of emission beams (radio versus gamma-ray) warrant further scrutiny, particularly with increasing sensitivity and observational capabilities of current astronomical instruments. The paper highlights the importance of utilizing comprehensive multi-wavelength observations to understand pulsar properties and their environmental interactions.

Future Prospects

Given the growing capability and applications of FAST, this paper sets a precedent for uncovering more such associations between pulsars and SNRs, potentially refining distance measurements and offering insights into the supernova explosion mechanisms. Further studies with enhanced datasets could also refine estimates of pulsar parameters, which might reveal anomalies or deviations in traditional pulsar models.

The paper of PSR J2016+3711 illustrates the synergy of radio and (non-detected) gamma-ray observations in understanding pulsar wind nebulae environments, emphasizing the potential for further multi-disciplinary astrophysical studies involving radio astronomy, X-ray, and gamma-ray observations in uncovering the complexities of pulsars embedded in dynamic, evolving remnants.