The FAST Discovery of a binary millisecond pulsar PSR~J1647-0156B (M12B) with a candidate cross matching algorithm

Abstract

We propose a pulsar candidate cross matching algorithm to sift radio pulsar search candidates from repeated observations of the same sky location such as globular clusters, high energy sources, or supernova remnants. Our method uses both the candidate spin period ($P$) and dispersion measure (DM) value; if two or more candidates from different observations have similar spin periods to within 1\%, and dispersion measure values within 10\%, they are likely to correspond to the same candidate detection. We have demonstrated the effectiveness of our method through the discovery of the pulsar M12B with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). This pulsar has a spin period of 2.76\,ms and a dispersion measure of $42.70 \pm 0.05\,\mathrm{cm}^{-3}~\mathrm{pc}$. This pulsar has a profile with three peaks, being faint, showing scintillation. It is in an approximately 0.53-day orbit. Our discovery indicates that more pulsars might be effectively discovered if the algorithm is applied to the search results from other archival globular cluster observations.

Figures (3)

• Figure 1: Diagnostic plot. Left upper: The detection plots of M12B. Lower left: Diagnostic scatter plot of M12B candidates in the P–DM parameter space. Each point’s horizontal coordinate represents the percentage deviation of the candidate’s measured period $P_i$ from the arithmetic mean period $\bar{P}$ of the M12B candidate group, calculated as: $\frac{P_i - \bar{P}}{\bar{P}} \times 100\%$. The vertical coordinate denotes the percentage deviation of the candidate’s measured dispersion measure $\mathrm{DM}_i$ from the group’s arithmetic mean $\overline{\mathrm{DM}}$, computed as: $\frac{\mathrm{DM}_i - \overline{\mathrm{DM}}}{\overline{\mathrm{DM}}} \times 100\%$. The origin (0%, 0%) in this panel corresponds to the group-average reference point $(\bar{P}, \overline{\mathrm{DM}})$, with all M12B candidate points plotted relative to this mean value. Right upper:the detection plots of RFI. Right lower:the diagnostic plot of RFI, displaying the distribution of RFI candidates in the identical P–DM percentage deviation parameter space as M12B for direct comparative analysis.
• Figure 2: Left:the detection plots of M12B. Right: the M12B signal from folding with partially timing solution, showing three peaks in the pulse profile.
• Figure 3: The distribution of orbital periods and semi-major axes of known binary pulsars. The double neutron star PSR J0737-3039A and B, and PSR J1946+2052 were near the red line which is for the equation $a_1 = \dfrac{0.01 \cdot c \cdot P_{\mathrm{b}}}{2\pi}$ that both of them may have 1% variation in spin periods due to the orbital movement. For other pulsars, the 1% upper limit is enough for the $\Delta P/P$.