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Abstract The equation of state (EOS) of dense strongly interacting matter can be probed by astrophysical observations of neutron stars (NS), such as X-ray detections of pulsars or the measurement of the tidal deformability of NSs during the inspiral stage of NS mergers. These observations constrain the EOS at most up to the density of the maximum-mass configuration,nTOV, which is the highest density that can be explored by stable NSs for a given EOS. However, under the right circumstances, binary neutron star (BNS) mergers can create a postmerger remnant that explores densities abovenTOV. In this work, we explore whether the EOS abovenTOVcan be measured from gravitational-wave or electromagnetic observations of the postmerger remnant. We perform a total of 25 numerical-relativity simulations of BNS mergers for a range of EOSs and find no case in which different descriptions of the matter abovenTOVhave a detectable impact on postmerger observables. Hence, we conclude that the EOS abovenTOVcan likely not be probed through BNS merger observations for the current and next generation of detectors.
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Exploring Massive Neutron Stars Towards the Mass Gap: Constraining the High Density Nuclear Equation of State
Due to the high-density nuclear matter equation of state (EOS) being as yet unknown, neutron stars (NSs) do not have a confirmed limiting “Chandrasekhar” type maximum mass. However, observations of NSs (PSR J1614-2230, PSR J0348+0432, PSR J0740+6620, PSR J0952–0607) indicate that the NS’s limiting mass, if there is any, could be well over 2M⊙. On the other hand, there seems to be an observational mass gap (of around 2.5−5M⊙ ) between the lightest black hole and the heaviest NS. Therefore, the “massive NSs” are prime candidates to fill that gap. Several NS EOSs have been proposed using both microscopic and phenomenological approaches. In this project, we look at a class of phenomenological nuclear matter EOSs—relativistic mean field models—and see what kind of NS is formed from them. We compute the max- imum mass supported by each model EOS to observe if the mass of the NS is indeed in the “massive” NS (>2M⊙) regime. We also observe the effects of including exotic particles (hyperons, Δs) in the NS EOS and how that affects the NS mass. However, only by introducing the magnetic field, i.e. for magnetized anisotro- pic NSs, we find the mass exceeding 2.5M⊙. Using tidal deformability constraints from gravitational wave observations, we place a further check on how physical the EOS and NSs are.
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- Award ID(s):
- 2012152
- PAR ID:
- 10555438
- Publisher / Repository:
- Astronomy Reports
- Date Published:
- Journal Name:
- Astronomy Reports
- Volume:
- 67
- Issue:
- S2
- ISSN:
- 1063-7729
- Page Range / eLocation ID:
- S199 to S206
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1134/S1063772923140214
