1,721,121 research outputs found
Relativistic correction to the r-mode frequency in light of multi-messenger constraints
No full textR-mode oscillations of rotating neutron stars are promising candidates for continuous gravitational wave (GW) observations. The r-mode frequencies for slowly rotating Newtonian stars are well-known and independent of the equation of state (EOS) but for neutron stars, several mechanisms can alter the r-mode frequency of which the relativistic correction is dominant and relevant for most of the neutron stars. The most sensitive searches for continuous GWs are those for known pulsars for which GW frequencies are in targeted narrow frequency bands of few Hz. In this study, we investigate the effect of several state-of-the-art multi-messenger constraints on the r-mode frequency for relativistic, slowly rotating, barotropic stars. Imposing these recent constraints on the EOS, we find that the r-mode frequency range is slightly higher from the previous study and the narrow band frequency range can increase upto 8-25% for the most promising candidate PSR J0537-6910 depending on the range of compactness. We also derive universal relations between r-mode frequency and dimensionless tidal deformability which can be used to estimate the dynamical tide of the r-mode resonant excitation during the inspiral signal. These results can be used to construct the parameter space for r-mode searches in gravitational wave data and also constrain the nuclear equation of state following a successful r-mode detection
Imposing multi-physics constraints at different densities on the Neutron Star Equation of State
No full textNeutron star matter spans a wide range of densities, from that of nuclei at the surface to exceeding several times normal nuclear matter density in the core. While terrestrial experiments, such as nuclear or heavy-ion collision experiments, provide clues about the behaviour of dense nuclear matter, one must resort to theoretical models of neutron star matter to extrapolate to higher density and finite neutron/proton asymmetry relevant for neutron stars. In this work, we explore the parameter space within the framework of the Relativistic Mean Field model allowed by present uncertainties compatible with state-of-the-art experimental data. We apply a cut-off filter scheme to constrain the parameter space using multi-physics constraints at different density regimes: chiral effective field theory, nuclear and heavy-ion collision data as well as multi-messenger astrophysical observations of neutron stars. Using the results of the study, we investigate possible correlations between nuclear and astrophysical observables
Tidal heating as a direct probe of strangeness inside neutron stars
Full text linkIt has been discussed whether viscous processes in neutron star matter during
a binary inspiral can damp out the tidal energy induced by the companion and
heat up the star. Earlier investigations concluded that this tidal heating is
negligible for normal neutron star matter. In this work, we suggest a novel
effect of tidal heating involving strange matter in the neutron star interior,
that can significantly heat up the star, and is potentially observable by
current and future gravitational wave detectors. We propose that this could
serve as a direct probe of strangeness in neutron stars.Comment: 8 pages, 5 figures, 1 tabl
Tidal dissipation in binary neutron star inspiral: bias study and modeling of frequency domain phase
No full textDuring the inspiral of a binary neutron star, viscous processes in the neutron star matter can damp out the tidal energy induced by its companion and convert it to thermal energy. This tidal dissipation/heating process introduces a net phase shift in the gravitational wave signal. In our recent work (Ghosh et al., Phys. Rev. D 109, 103036 (2024)), we showed that tidal dissipation from bulk viscosity originating from the non-leptonic weak interactions involving hyperons could have a detectable phase shift in the gravitational-wave (GW) signal in the next-generation GW detectors. In this work, we model the dephasing due to tidal dissipation in a post-Newtonian (PN) expansion and incorporate this in gravitational waveforms for equal mass binary neutron stars. We then estimate the systematic bias incurred in tidal deformability measurements in simulated signal injection studies when this physical effect is not accounted for in waveform models. Lastly, we perform a full Bayesian parameter estimation with our model to show how accurately we can measure the additional phase due to tidal dissipation in future GW observations and discuss its significance in extreme matter studies
Effect of magnetic fields on Urca rates in neutron star mergers
No full textIsospin-equilibrating weak processes, called "Urca" processes, are of fundamental importance in astrophysical environments like (proto-)neutron stars, neutron star mergers, and supernovae. In these environments, matter can reach high temperatures of tens of MeVs and be subject to large magnetic fields. We thus investigate Urca rates at different temperatures and field strengths by performing the full temperature and magnetic-field dependent rate integrals for different equations of state. We find that the magnetic fields play an important role at temperatures of a few MeV, especially close to or below the direct Urca threshold, which is softened by the magnetic field. At higher temperatures, the effect of the magnetic fields can be overshadowed by the thermal effects. We observe that the magnetic field more strongly influences the neutron decay rates than the electron capture rates, leading to a shift in the flavor equilibrium
Multi-physics constraints at different densities to probe nuclear symmetry energy in hyperonic neutron stars
Full text linkThe appearance of strangeness in the form of hyperons within the inner core
of neutron stars is expected to affect its detectable properties such as its
global structure or gravitational wave emission. In this work, we explore the
parameter space of hyperonic stars within the framework of the Relativistic
Mean Field model allowed by present uncertainties in state-of-the-art nuclear
and hypernuclear experimental data. We impose multi-physics constraints at
different density regimes to restrict the parameter space: Chiral effective
field theory, heavy-ion collision data as well as multi-messenger astrophysical
observations of neutron stars. We investigate possible correlations between
empirical nuclear and hypernuclear parameters, particularly the symmetry energy
and its slope, with observable properties of neutron stars. We do not find a
correlation for the hyperon parameters and the astrophysical data. However, the
inclusion of hyperons generates a tension between the astrophysical and heavy
ion data constraining considerable the available parameter space.Comment: 26 pages, 7 figure
Constraining the equation of state of hybrid stars using recent information from multidisciplinary physics
Full text linkAt the ultra-high densities existing in the core of neutron stars, it is
expected that a phase transition from baryonic to deconfined quark matter may
occur. Such a phase transition would affect the underlying equation of state
(EoS) as well as the observable astrophysical properties of neutron stars.
Comparison of EoS model predictions with astronomical data from multi-messenger
signals then provides us an opportunity to probe the behaviour of dense matter.
In this work, we restrict the allowed parameter space of EoS models in neutron
stars for both nucleonic (relativistic mean field model) and quark matter (bag
model) sectors by imposing state-of-the-art constraints from nuclear
calculations, multi-messenger astrophysical data and perturbative QCD (pQCD).
We systematically investigate the effect of each constraint on the parameter
space of uncertainties using a cut-off filter scheme, as well as the
correlations among the parameters and with neutron star astrophysical
observables. Using the constraints, we obtain limits for maximum NS mass,
maximum central density, as well as for NS radii and tidal deformability.
Although pQCD constraints are only effective at very high densities, they
significantly reduce the parameter space of the quark model. We also conclude
that astrophysical data supports high values of the bag parameter B and
disfavors the existence of a pure quark matter core in hybrid stars.Comment: 16 pages, 11 figures, 2 table
g-mode Oscillations in Neutron Stars with Hyperons
Full text linkA common alternative to the standard assumption of nucleonic composition of
matter in the interior of a neutron star is to include strange baryons,
particularly hyperons. Any change in composition of the neutron star core has
an effect on g-mode oscillations of neutron stars, through the compositional
dependence of the equilibrium and adiabatic sound speeds. We study the core
g-modes of a neutron star contaning hyperons, using a variety of relativistic
mean field models of dense matter that satisfy observational constraints on
global properties of neutron stars. Our selected models predict a sharp rise in
the g-mode frequencies upon the onset of strange baryons. Should g-modes be
observed in the near future, their frequency could be used to test the presence
of hyperonic matter in the core of neutron stars.Comment: 17 pages, 7 figure
R-modes as a New Probe of Dark Matter in Neutron Stars
Full text linkIn this work, we perform the first systematic investigation of effects of the
presence of dark matter on -mode oscillations in neutron stars (NSs). Using
a self-interacting dark matter (DM) model based on the neutron decay anomaly
and a hadronic model obtained from the posterior distribution of a recent
Bayesian analysis, we impose constraints on the DM self-interaction strength
using recent multimessenger astrophysical observations. We also put new
constraints on the DM fraction for this model of DM. The constrained DM
interaction strength is then used to estimate DM self-interaction cross section
and shear viscosity resulting from DM, which is found to be several orders of
magnitude smaller than shear viscosity due to hadronic matter. Assuming
chemical equilibrium among DM fermions and neutrons, we estimate the bulk
viscosity resulting from the dark decay of neutrons considering different
scenarios for the temperature dependence of the reaction rate and investigate
the effect on the -mode instability window. We conclude that DM shear and
bulk viscosity may significantly modify the -mode instability window
compared with the minimal hadronic viscosities, depending on the temperature
dependence of the process. We also found that for the window to be compatible
with the X-ray and pulsar observational data, the rate for the dark decay
process must be fast.Comment: 29 pages, 12 figures, 1 table. Manuscript published in JCAP. This is
the Accepted Manuscript version of an article accepted for publication in
JCAP. Neither SISSA Medialab Srl nor IOP Publishing Ltd is responsible for
any errors or omissions in this version of the manuscript or any version
derived from it. The Version of Record is available online at
https://doi.org/10.1088/1475-7516/2023/12/00
Investigating tidal heating in neutron stars via gravitational Raman scattering
Full text linkWe present a scattering amplitude formalism to study the tidal heatingeffects of nonspinning neutron stars incorporating both worldline effectivefield theory and relativistic stellar perturbation theory. In neutron stars,tidal heating arises from fluid viscosity due to various scattering processesin the interior. It also serves as a channel for the exchange of energy andangular momentum between the neutron star and its environment. In the interiorof the neutron star, we first derive two master perturbation equations thatcapture fluid perturbations accurate to linear order in frequency. Remarkably,these equations receive no contribution from bulk viscosity due to a peculiaradiabatic incompressibility which arises in stellar fluid for non-barotropicperturbations. In the exterior, the metric perturbations reduce to theRegge-Wheeler (RW) equation which we solve using the analyticalMano-Suzuki-Takasugi (MST) method. We compute the amplitude for gravitationalwaves scattering off a neutron star, also known as gravitational Ramanscattering. From the amplitude, we obtain expressions for the electricquadrupolar static Love number and the leading dissipation number to all ordersin compactness. We then compute the leading dissipation number for variousrealistic equation-of-state(s) and estimate the change in the number ofgravitational wave cycles due to tidal heating during inspiral in theLIGO-Virgo-KAGRA (LVK) band.<br
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