High-Energy Emission of the First Millisecond Pulsar

TL;DR

This paper presents detailed X-ray and gamma-ray observations of the first millisecond pulsar, revealing its non-thermal emission, pulse profile characteristics, and implications for high magnetic field pulsar models.

Contribution

It provides new observational constraints on the high-energy emission properties of the first millisecond pulsar, including spectral and timing analysis in X-ray and gamma-ray bands.

Findings

X-ray emission is non-thermal and nearly 100% pulsed.

Gamma-ray spectrum fits a power-law with photon index 2.38.

Pulse profiles in X-ray and gamma-ray are similar and aligned with radio peaks.

Abstract

We report on X-ray and gamma-ray observations of the millisecond pulsar B1937+21 taken with the Chandra X-ray Observatory, XMM-Newton, and the Fermi Large Area Telescope. The pulsar X-ray emission shows a purely non-thermal spectrum with a hard photon index of 0.9+/-0.1, and is nearly 100% pulsed. We found no evidence of varying pulse profile with energy as previously claimed. We also analyzed 5.5 yr of Fermi survey data and obtained much improved constraints on the pulsar's timing and spectral properties in gamma-rays. The pulsed spectrum is adequately fitted by a simple power-law with a photon index of 2.38+/-0.07. Both the gamma-ray and X-ray pulse profiles show similar two-peak structure and generally align with the radio peaks. We found that the aligned profiles and the hard spectrum in X-rays seem to be common properties among millisecond pulsars with high magnetic fields at the light cylinder. We discuss a possible physical scenario that could give rise to these features.