Gravitational waves or deconfined quarks: What causes the premature collapse of neutron stars born in short gamma-ray bursts?
Gravitational waves or deconfined quarks: What causes the premature collapse of neutron stars born in short gamma-ray bursts?
We infer the collapse times of long-lived neutron stars into black holes using the x-ray afterglows of 18 short gamma-ray bursts. We then apply hierarchical inference to infer properties of the neutron star equation of state and dominant spin-down mechanism. We measure the maximum non-rotating neutron star mass MTOV=2.31-0.21 +0.36M⊙ and constrain the fraction of remnants spinning down predominantly through gravitational-wave emission to η=0.69-0.39 +0.21 with 68% uncertainties. In principle, this method can determine the difference between hadronic and quark equation of states. In practice, however, the data is not yet informative with indications that these neutron stars do not have hadronic equation of states at the 1σ level. These inferences all depend on the underlying progenitor mass distribution for short gamma-ray bursts produced by binary neutron star mergers. The recently announced gravitational-wave detection of GW190425 suggests this underlying distribution is different from the locally measured population of double neutron stars. We show that MTOV and η constraints depend on the fraction of binary mergers that form through a distribution consistent with the locally measured population and a distribution that can explain GW190425. The more binaries that form from the latter distribution, the larger MTOV needs to be to satisfy the x-ray observations. Our measurements above are marginalized over this unknown fraction. If instead, we assume GW190425 is not a binary neutron star merger, i.e., the underlying mass distribution of double neutron stars is the same as observed locally, we measure MTOV=2.26-0.17 +0.31M⊙.
Sarin, Nikhil
bfde4e6e-0c6d-4f0f-898e-7ec34b4602ef
Lasky, Paul D.
21c4d51d-89db-4dc1-b5f9-cd9835d54fad
Ashton, Gregory
a8cec4b1-3c98-4b28-af2a-1e37cb3b9f2a
15 March 2020
Sarin, Nikhil
bfde4e6e-0c6d-4f0f-898e-7ec34b4602ef
Lasky, Paul D.
21c4d51d-89db-4dc1-b5f9-cd9835d54fad
Ashton, Gregory
a8cec4b1-3c98-4b28-af2a-1e37cb3b9f2a
Sarin, Nikhil, Lasky, Paul D. and Ashton, Gregory
(2020)
Gravitational waves or deconfined quarks: What causes the premature collapse of neutron stars born in short gamma-ray bursts?
Physical Review D, 101 (6).
(doi:10.1103/PhysRevD.101.063021).
Abstract
We infer the collapse times of long-lived neutron stars into black holes using the x-ray afterglows of 18 short gamma-ray bursts. We then apply hierarchical inference to infer properties of the neutron star equation of state and dominant spin-down mechanism. We measure the maximum non-rotating neutron star mass MTOV=2.31-0.21 +0.36M⊙ and constrain the fraction of remnants spinning down predominantly through gravitational-wave emission to η=0.69-0.39 +0.21 with 68% uncertainties. In principle, this method can determine the difference between hadronic and quark equation of states. In practice, however, the data is not yet informative with indications that these neutron stars do not have hadronic equation of states at the 1σ level. These inferences all depend on the underlying progenitor mass distribution for short gamma-ray bursts produced by binary neutron star mergers. The recently announced gravitational-wave detection of GW190425 suggests this underlying distribution is different from the locally measured population of double neutron stars. We show that MTOV and η constraints depend on the fraction of binary mergers that form through a distribution consistent with the locally measured population and a distribution that can explain GW190425. The more binaries that form from the latter distribution, the larger MTOV needs to be to satisfy the x-ray observations. Our measurements above are marginalized over this unknown fraction. If instead, we assume GW190425 is not a binary neutron star merger, i.e., the underlying mass distribution of double neutron stars is the same as observed locally, we measure MTOV=2.26-0.17 +0.31M⊙.
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Published date: 15 March 2020
Additional Information:
Funding Information: We are grateful to Colm Talbot for helpful discussions on population inference. We also thank Eric Thrane for his insightful comments on selection effects. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. N. S. is supported through an Australian Postgraduate Award. P. D. L. is supported through Australian Research Council Future Fellowship FT160100112 and ARC Discovery Project No. DP180103155. Publisher Copyright: © 2020 American Physical Society.
M1 - 063021
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Local EPrints ID: 508006
URI: http://eprints.soton.ac.uk/id/eprint/508006
ISSN: 2470-0010
PURE UUID: adcd2b1c-7d9e-40ed-9740-c61556b42376
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Date deposited: 09 Jan 2026 17:41
Last modified: 10 Jan 2026 05:27
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Author:
Nikhil Sarin
Author:
Paul D. Lasky
Author:
Gregory Ashton
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