# Implications from GW170817 for $\Delta$-isobar admixed hypernuclear compact stars

## TL;DR

This paper investigates how $\Delta$ isobars influence the dense matter equation of state and the structure of compact stars, demonstrating compatibility with GW170817 tidal deformability data and suggesting hypernuclear stars with $\Delta$ isobars are plausible.

## Contribution

It introduces a covariant density functional approach to include $\Delta$ isobars in hypernuclear star models and compares predictions with gravitational wave observations.

## Key findings

- $\Delta$ isobars soften the equation of state, aligning models with small star radii.
- GW170817 tidal deformability data supports the existence of hypernuclear stars with $\Delta$ isobars.
- The event is consistent with mergers involving stars containing both hyperons and $\Delta$ isobars.

## Abstract

The effects of $\Delta$ isobars on the equation of state of dense matter and structure of compact stars (CSs) are explored within the covariant density functional theory and confronted with the data on tidal deformability (TD) extracted from the GW170817 event. We show that the presence of $\Delta$ isobars substantially softens the tension between the predictions of the hypernuclear density functionals and the inference from the observations of relatively small radius and small TD of canonical mass CSs. The TDs deduced from GW170817 are compatible with the existence of hypernuclear CSs containing an admixture of $\Delta$ isobars. We thus argue that the GW170817 event is consistent with a merger of a binary CS system having both strangeness (hyperons) and $\Delta$ isobars in the stellar core.