The low-mass X-ray binary-millisecond radio pulsar birthrate problem revisited

TL;DR

This paper revisits the birthrate discrepancy between low-mass X-ray binaries and millisecond radio pulsars, proposing that faint LMXBs could account for the observed MRP population and resolve the longstanding problem.

Contribution

It introduces a new perspective that faint LMXBs significantly contribute to the MRP population, addressing the birthrate mismatch.

Findings

Calculated LMXB and MRP birthrates using semi-analytical and numerical methods.

Identified faint LMXBs as a major progenitor population for MRPs.

Suggested that faint LMXBs could explain the observed MRP numbers in the Galaxy.

Abstract

We investigate the birthrate problem for low-mass X-ray binaries (LMXBs) and millisecond radio pulsars (MRPs) in this paper. We consider intermediate-mass and low-mss X-ray binaries (I/LMXBs) as the progenitors of MRPs, and calculate their evolutionary response to the cosmic star formation rate (SFR) both semi-analytically and numerically. With typical value (~1 Gyr) of the LMXB lifetime, one may expect comparable birthrates of LMXBs and MRPs, but the calculated number of LMXBs is an order of magnitude higher than observed in the Galaxy. Instead, we suggest that the birthrate problem could be solved if most MRPs have evolved from faint rather bright LMXBs. The former may have a population of ~ 104 in the Galaxy.