Illuminating Hidden Pulsars: Scintillation-Enhanced Discovery of Two Binary Millisecond Pulsars in M13 with FAST

TL;DR

This study used FAST radio telescope data and scintillation effects to discover two faint binary millisecond pulsars in M13, revealing systems that are typically hidden and demonstrating the importance of scintillation in pulsar detection.

Contribution

The paper introduces a scintillation-enhanced search method using FFT techniques on FAST data, leading to the discovery of two previously undetected binary millisecond pulsars in M13.

Findings

Discovered two binary millisecond pulsars in M13 during scintillation-brightened states.

One pulsar is a black widow system with a very low-mass companion.

Detected pulsars exhibit significant apparent acceleration, with one detected in only 2 of 84 observations.

Abstract

We conducted a sensitive acceleration search using Fast Fourier Transform (FFT) techniques on full-length and segmented data from 84 observations of the globular cluster M13 with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Employing a low detection threshold (2 $\sigma$) to maximize sensitivity to faint pulsars, here we report the discovery of two binary millisecond pulsars: J1641+3627G (M13G) and J1641+3627H (M13H). Both pulsars were detected during scintillation-brightened states, revealing systems that would otherwise remain undetected. For M13G, we obtained a phase-connected timing solution spanning 6.4 years, identifying it as a black widow system with an orbital period of 0.12 days hosting an extremely low-mass companion ($\sim 9.9\times 10^{-3}~{ M}_\odot$), though no eclipses were observed. M13H, however, shows significant apparent acceleration but was detected in only 2 of 84 observations; its extremely low detection rate currently prevents constraints on orbital parameters or classification.