Gamma-radiation sky maps from compact binaries

TL;DR

This paper models gamma-ray sky maps and light curves from neutron stars in binaries and isolation, revealing how magnetic field complexity influences observable emission patterns and providing tools for rapid exploration of binary systems.

Contribution

It introduces new heuristics for inferring pulsar magnetic field structures from gamma-ray observations and applies the Separatrix Layer model to binary systems and merger scenarios.

Findings

Double-peak light curves can arise from complex multipole magnetic fields.

Binary systems exhibit distinct gamma-ray patterns depending on observer orientation.

Predicted gamma-ray signatures vary significantly before black hole-neutron star mergers.

Abstract

We study sky maps and light curves of gamma-ray emission from neutron stars in compact binaries, and in isolation. We briefly review some gamma-ray emission models, and reproduce sky maps from a standard isolated pulsar in the Separatrix Layer model. We consider isolated pulsars with several variations of a dipole magnetic field, including superpositions, and predict their gamma-ray emission. Our results provide new heuristics on what can and cannot be inferred about the magnetic field configuration of pulsars from high-energy observations. We find that typical double-peak light curves can be produced by pulsars with significant multipole structure beyond a single dipole. For binary systems, we also present a simple approximation that is useful for rapid explorations of binary magnetic field structure. Finally, we predict the gamma-ray emission pattern from a compact black hole-neutron star binary moments before merger by applying the Separatrix Layer model to data simulated in full general relativity; we find that face-on observers receive little emission, equatorial observers see one broad peak, and more generic observers typically see two peaks.