Discovery and timing of pulsar J2016+3711 in supernova remnant CTB 87 with FAST

Abstract

We report on our discovery of the radio pulsar, PSR J2016+3711, in supernova remnant (SNR) CTB 87, with a ~10.8σ 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 per cent of the peak flux density of about 28.1^○ and an effective width of about 32.2^○. 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 ≲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 × 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 × 10¹² 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 towards the X-ray counterpart of the gamma-ray binary HESS J1832-093 proximate to SNR G22.7-00.2 but found no signal.