Thermal and Non-thermal radiation from pulsars: hints of physics

TL;DR

This paper explores how thermal and non-thermal radiation from pulsars can reveal the nature of their dense matter, proposing that quark-cluster stars with self-bound surfaces better explain observed phenomena than traditional neutron stars.

Contribution

It introduces the idea that pulsar emissions suggest the existence of self-bound quark-cluster stars, offering explanations for surface features, emission phenomena, and implications for supernova mechanisms.

Findings

Non-thermal emissions imply strong particle binding on polar caps.

Thermal spectra suggest bare, atmosphere-less surfaces.

Mass and radius measurements support a stiff, self-bound matter model.

Abstract

Thermal and non-thermal radiation from pulsars carries significant information from surface and would have profound implications on the state of dense matter in compact stars. For the non-thermal radio emission, subpulse drifting phenomena suggest the existence of Ruderman-Sutherland-like gap-sparking and strong binding of particles on pulsar polar caps. While conventional neutron star models can hardly provide such a high binding energy, the strong self-bound surface of quark-cluster stars can naturally solve this problem. As for the thermal one, the featureless X-ray spectra of pulsars may indicate a bare surface without atmosphere, and the ultrarelativistic fireball of gamma-ray bursts and supernovae would also require strong self-bound surfaces. Recent achievements in measuring pulsar mass and mass-radius relation further indicate a stiff equation of state and a self-bound surface. Therefore, we conjecture that matters inside pulsar-like compact stars could be in a quark-cluster phase. The surface of quark-cluster stars is chromatically confined and could initially be bare. Such a surface can not only explain above features, but may also promote a successful core-collapse supernova, and the hydro-cyclotron oscillation of the electron sea above the surface could be responsible for those absorption features detected in the X-ray spectrum.