Quark-nova compact remnants: Observational signatures in astronomical data and implications to compact stars

TL;DR

This paper explores observational signatures of quark stars formed after quark-novae, proposing models for their bursting activity, spectral features, and distinguishing characteristics from magnetars, with implications for understanding compact star remnants.

Contribution

It introduces a model for quark star signatures, including bursting activity and spectral features, differentiating them from magnetars and explaining observed phenomena.

Findings

Quark stars can produce X-ray and gamma-ray bursts via accretion events.

Spectral lines can originate from r-process atomic material.

An anti-glitch in an AXP can be explained by angular momentum transfer from a surrounding disk.

Abstract

Quark-novae leave behind quark stars with a surrounding metal-rich fall-back (ring-like) material. These compact remnants have high magnetic fields and are misconstrued as magnetars; however, several observational features allow us to distinguish a quark star (left behind by a quark-nova) from a neutron star with high magnetic field. In our model, bursting activity is expected from intermittent accretion events from the surrounding fall-back debris leading to X-ray bursts (in the case of a Keplerian ring) or gamma ray bursts (in the case of a co-rotating shell). The details of the spectra are described by a constant background X-ray luminosity from the expulsion of magnetic flux tubes which will be temporarily buried by bursting events caused by accretion of material onto the quark star surface. These accretion events emit high energy photons and heat up the quark star and surrounding debris leading to hot spots which may be observable as distinct blackbodies. Additionally, we explain observed spectral line features as atomic lines from r-process material and explain an observed anti-glitch in an AXP as the transfer of angular momentum from a surrounding Keplerian disk to the quark star.