Impact of soft versus hard equations of state on hybrid stars

Abstract

The nuclear stiffness as a dominant contribution of nuclear symmetry energy is analyzed on the properties of compact stars considering constraints from nuclear physics and astrophysics. A compact star can be a neutron star composed only of nuclear matter or a hybrid star with a quark core. Two typical models (soft and stiff) are considered for the nuclear equation of state, and for the hybrid one, a parameterized first-order phase transition approach, completed with a linear quark matter equation of state, is implemented. We show that the phase transition reduces the tension between GW170817 and NICER observations, and we illustrate the impact of nuclear stiffness for the understanding of the nature of the binary system in GW170817. The implication on nuclear symmetry energy is also discussed. We also confirm our previous findings that the GW170817 waveform is best described as a binary HS with a low-density onset of stiff quark matter. This could also be interpreted as a quarkyonic cross-over.

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BibTeX RIS

BibTeX

@misc{bozkurt2026impact,
  title = {{Impact of soft versus hard equations of state on hybrid stars}},
  author = {K. Bozkurt and Jérôme Margueron and Elias Khan and Haşim Zahid Güven},
  howpublished = {HAL},
  year = {2026},
  month = sep,
  url = {https://hal.science/hal-05847004v1},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Impact of soft versus hard equations of state on hybrid stars
AU  - K. Bozkurt
AU  - Jérôme Margueron
AU  - Elias Khan
AU  - Haşim Zahid Güven
PY  - 2026
DA  - 2026/09/21
PB  - HAL
UR  - https://hal.science/hal-05847004v1
AB  - The nuclear stiffness as a dominant contribution of nuclear symmetry energy is analyzed on the properties of compact stars considering constraints from nuclear physics and astrophysics. A compact star can be a neutron star composed only of nuclear matter or a hybrid star with a quark core. Two typical models (soft and stiff) are considered for the nuclear equation of state, and for the hybrid one, a parameterized first-order phase transition approach, completed with a linear quark matter equation of state, is implemented. We show that the phase transition reduces the tension between GW170817 and NICER observations, and we illustrate the impact of nuclear stiffness for the understanding of the nature of the binary system in GW170817. The implication on nuclear symmetry energy is also discussed. We also confirm our previous findings that the GW170817 waveform is best described as a binary HS with a low-density onset of stiff quark matter. This could also be interpreted as a quarkyonic cross-over.
ER  -

Abstract

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