Millisecond Pulsars in M2: New discoveries and a detailed timing analysis

TL;DR

This paper reports the discovery of two new millisecond pulsars in globular cluster M2, provides detailed timing and emission measurements, and combines optical and radio data to study their properties and cluster environment.

Contribution

It presents the first phase-coherent timing solutions for M2 pulsars, measures their orbital parameters precisely, and identifies the youngest white dwarf companion in a globular cluster binary.

Findings

Discovery of two new binary millisecond pulsars in M2

First phase-coherent timing solutions for M2 pulsars

Identification of a young white dwarf companion with a cooling age of ~10 Myr

Abstract

Globular clusters (GCs) offer a unique environment for discovering and studying millisecond pulsars. In this paper, we present a multi-epoch search and detailed timing analysis of millisecond pulsars in the GC M2, using the Five-hundred-meter Aperture Spherical Telescope. We have discovered two new binary millisecond pulsars in M2, designated M2F and M2G, respectively. We provide measurements of the emission properties of all known pulsars in M2, including their polarization profiles, rotation measures, flux densities, scintillation characteristics, and so forth. In particular, we report the first rotation measure at the distance and direction of this cluster. Additionally, we report the first phase-coherent timing solutions for the M2 pulsars. From our Bayesian timing analysis, we have measured their spin and orbital parameters with high precision, including the advance of periastron for M2A and M2E indicating total system masses of 1.75(13) and 1.80(5) solar masses respectively. Using archival data from the Hubble Space Telescope, we have identified an optical counterpart of M2C, which is likely the white dwarf companion of the pulsar. By combining results from optical and radio observations, we have reconstructed the binary evolution track of this system and estimated the cooling age of the companion to be approximately 10\,Myr, making it the youngest white dwarf in any known GC binary pulsars. Furthermore, using the spin period derivatives of M2 pulsars, we have investigated the gravitational potential of the cluster and found that our results strongly support the latest central-stellar-velocity dispersion measurement in M2.