
2
from the quadrupolar tides, followed by higher-order
octupolar (Λ3) and hexadecapolar (Λ4) terms [18, 24].
Recent waveform models have been updated to consider
the effect of the higher order tidal parameters Λ3, Λ4
and also the magnetic type deformation (quadrupolar
magnetic Σ2in the GW phase [24, 25]. In most
analyses, the tides are considered adiabatic, ie. the GW
frequency is much lower than the NS resonant oscillation
mode frequency. However, recent efforts largely support
the excitation of NS fundametal modes (f-modes) in the
late inspiral [26–31]. In a frequency domain model, the
dynamical tidal contribution to the GW phase due to the
excitation of f-modes appears at 8 PN order [18, 32] and
depends upon the f-mode frequency. Since the additional
tidal deformability parameters and the f-mode dynam-
ical phase contribute at high PN orders, they are often
dropped while constructing waveform approximants.
However, the f-mode dynamical tidal correction has been
shown to significantly affect the inference of NS proper-
ties from a binary due to its resonance behaviour [33, 34].
Previous works have suggested that there exist EoS-
insensitive universal relations (UR) between Λ2and each
of Λ3, Λ4, and Σ3( hereafter referred as ‘multipole Love’
relation) [35–37]. Similarly, URs exist between the
f-mode frequency and tidal parameters [38] ( hereafter
referred as ‘f-Love’ relation). This allows the additional
contribution due to higher order tidal parameters or
f-mode parameters to be considered without having to
actually sample over them in a parameter estimation
run, reducing the search parameter space. Additionally,
there exists UR involving stellar compactness and
quadrupole tidal parameters, which can be used to infer
NS radius from the measured mass and quadrupole tidal
parameters from a BNS event [39]. In this work, we will
only be interested in the URs mentioned above. There
also exist URs involving the combination of Λ2and mass
ratio qof the binaries, known as ‘binary Love relations,’
as well as URs involving NS spin which reduces effort in
measuring the NS tidal parameter (and NS radius) in a
BNS event [40–46] 1.
The existing URs are employed by considering a few
theoretical EoS models and some of the selective EoSs
are now incompatible with the current astrophysical
constraints [35, 37–39]. Also, the existing URs do not
consider the EoS uncertainties resulting from the nuclear
parameters. In this work, we improve the multipole
Love and f-Love URs relevant for GW astronomy and
investigate the impact of the updated URs by analyzing
the BNS event GW170817 and performing several
injection and recovery studies with the future GW
detector configurations. This work is organized in the
1Recently a new EoS insensitive approach involving the NS mass
and tidal deformability is proposed to constrain NS properties
from a GW event [47].
following way. In section II we discuss the choices of
Eos, followed by the description of the methodology to
solve for multipole tidal parameters and to solve for the
NS f-mode characteristics. We compile our results in
Section III and summarise our conclusions in Section IV .
II. METHOD
A. Choices of Equations of State
The EoS is essentially the relation between the pressure
(p) and density (ρ) (or energy density ), i.e., p=p().
As described in Section I, different physical motivations
develop a diverse family of EoSs depending upon the
physical descriptions of the NS matter. In this work,
we consider a wide range of EoSs based upon different
physical descriptions. They are discussed below:
a. Relativistic Mean Field (RMF) Models: RMF
models are phenomenological models where baryon-
baryon interaction is mediated via exchange of mesons.
The Lagrangian density describes the interaction be-
tween baryons through the exchange of mesons. The
complete description of the Lagrangian density for
nucleonic (npeµ) and nucleon-hyperon (npeµY ) mat-
tered NS, and hence the EoS within the RMF model
considered in this work can be found in [48]. The
parameters of the RMF model are calibrated to the
nuclear and hypernuclear parameters at saturation:
nuclear saturation density (n0), the binding energy
per nucleon (E/A or Esat), incompressibility (K), the
effective nucleon mass (m∗), symmetry energy (J) and
slope of symmetry energy (L) at saturation. Hyperon
coupling constants are fixed using hyperon nucleon
potential depths (UY) or using symmetry properties. We
consider the total uncertainty ranges in the saturation
parameters resulting from nuclear and hypernuclear
experiments, summarized in Table I [49].
b. Selective EoSs: Along with the RMF mod-
els with nucleonic and hyperonic mattered EoSs, we
consider many realistic EoSs. The realistic EoSs are
taken either from CompOSE database [51–53] or
from LALSimulation [54]. The considered realistic
EoSs are APR4, APR3 [6, 55], SLy4 [56], BL [57],
DD2(GPPVA) [58], SRO-APR [59], BSk22 [60, 61],
WFF1 [62], MPA1 [63]. We also consider the Soft and
Stiff EoS from [5]. In Figure 1a, though the Stiff-EoS
terminates at earlier energy density, it is sufficient to
reach the maximum stable NS mass the EoS model
can reproduce [5]. To capture the hypothesis of a
deconfined quark phase in the interior of the NS core,
we account for some realistic hybrid EoSs containing the
quark phase in the interior. The selective hybrid EoS
models are BFH-D [64, 65], KBH (QHC21 −AT) [66],
JJ-VQCD [67] and OOS-DD2(FRG) [68]. We do not
consider the EoSs regarding quark stars only, as they