Exploring the effects of Delta Baryons in magnetars

TL;DR

This study investigates how the inclusion of spin-3/2 Delta baryons affects the microscopic composition and macroscopic properties of magnetars under strong magnetic fields, revealing they are favored over hyperons without softening the EoS.

Contribution

First analysis of Delta baryons' effects in magnetars considering Landau levels and anomalous magnetic moments using relativistic models.

Findings

Delta baryons are favored over hyperons in magnetar matter.

Their presence increases isospin asymmetry and decreases spin polarization.

Delta baryons do not significantly soften the equation of state or reduce magnetar mass.

Abstract

Strong magnetic fields can modify the microscopic composition of matter with consequences on stellar macroscopic properties. Within this context, we study, for the first time, the possibility of the appearance of spin-3/2 $\Delta$ baryons in magnetars. We make use of two different relativistic models for the equation of state of dense matter under the influence of strong magnetic fields considering the effects of Landau levels and the anomalous magnetic moment (AMM) proportional to the spin of all baryons and leptons. In particular, we analyze the effects of the AMM of $\Delta$ baryons in dense matter for the first time. {We also obtain global properties corresponding to the EoS models numerically and study the corresponding role of the $\Delta$ baryons.} We find that they are favored over hyperons, which causes an increase in isopin asymmetry and a decrease in spin polarization. We also find that, contrary to what generally occurs when new degrees of freedom are introduced, the $\Delta$s do not make the EoS significantly softer and magnetars less massive. Finally, the magnetic field distribution inside a given star is not affected by the presence of $\Delta$s.