19 research outputs found
Multipole tidal effects in the post-Newtonian gravitational-wave phase of compact binary coalescences
We present the multipole component form of the gravitational wave tidal phase
for compact binary coalescences (MultipoleTidal), which consists of the mass
quadrupole, the current quadrupole, and the mass octupole moments. We
demonstrate the phase evolution and the phase difference between the tidal
multipole moments (MultipoleTidal) and the mass quadrupole (PNTidal) as well as
the numerical-relativity calibrated model (NRTidalv2). We find the
MultipoleTidal gives a larger phase shift than the PNTidal, and is closer to
the NRTidalv2. We compute the matches between waveform models to see the impact
of the tidal multipole moments on the gravitational wave phases. We find the
MultipoleTidal gives larger matches to the NRTidalv2 than the PNTidal, in
particular, for high masses and large tidal deformabilities. We also apply the
MultipoleTidal model to binary neutron star coalescence events GW170817 and
GW190425. We find that the current quadrupole and the mass octupole moments
give no significant impact on the inferred tidal deformability.Comment: 14 pages, 7 figures. Minor improvements and typos correcte
Follow-up analyses of the binary-neutron-star signals GW170817 and GW190425 by using post-Newtonian waveform models
We reanalyze the binary-neutron-star signals, GW170817 and GW190425, focusing
on the inspiral regime to avoid uncertainties on waveform modeling in the
postinspiral regime. We use post-Newtonian waveform models as templates, which
are theoretically rigid and efficiently describe the inspiral regime. We study
potential systematic difference in estimates of the binary tidal deformability
by using different descriptions for the point-particle
dynamics and tidal effects. We find that the estimates of
show no significant systematic difference among three models for the
point-particle parts: TF2, TF2g, and TF2+, when they employ the same tidal
model. We compare different tidal descriptions given by different
post-Newtonian orders in the tidal phase. Our results indicate that the
estimates of slightly depend on the post-Newtonian order in
the tidal phase and an increase in the tidal post-Newtonian order does not lead
to a monotonic change in the estimate of . We also compare the
estimate of obtained by the post-Newtonian tidal model and
numerical-relativity calibrated tidal models. We find that the post-Newtonian
model gives slightly larger estimate of and wider posterior
distribution than the numerical-relativity calibrated models. According to
Bayesian model comparison, it is difficult to identify a preference among the
post-Newtonian orders by relying on the GW170817 and GW190425 data. Our results
indicate no preference among numerical-relativity calibrated tidal models over
the post-Newtonian model. Additionally, we present constraints on
equation-of-state models for neutron stars with the post-Newtonian model, which
show that the GW170817 data disfavor less compact models, though they are
slightly weaker constraints than the numerical-relativity calibrated tidal
models.Comment: 18 pages, 9 figures, Accepted for publication in Physical Review
Searching for gravitational wave echoes from black hole binary events in the third observing run of LIGO, Virgo, and KAGRA collaborations
Gravitational wave echo signals have been proposed as evidence for the
modification of the spacetime structure near the classical event horizon. These
signals are expected to occur after the mergers of compact binaries as a
sequence of weak pulse-like signals. Some studies have shown evidence of the
echo signals from several binary black hole merger events. On the other hand,
the other studies have shown the low significance of such signals from various
events in the first, second and third observing runs (O1, O2 and O3). Our
previous study also shows the low significance of echo signals from events in
O1 and O2, though, we observe that more than half of the events have p-value
smaller than 0.1 when the simply modeled waveform is used for the analysis.
Since there are only nine events appropriate for this analysis in O1 and O2, it
is necessary to analyze more events to evaluate the significance statistically.
In this study, we search for echo signals from binary black hole events
observed during O3 operated by LIGO, Virgo and KAGRA collaborations. We perform
the template-based search by using two different models for echo signal
templates: simply modeled one and physically motivated one. Our results show
that the distributions of p-values for all events analyzed in this study are
consistent with the noise distribution. This means that no significant echo
signals are found for both models from O3 events.Comment: 11 page
Halo models in modified gravity theories with self-accelerated expansion
We investigate the structure of halos in the sDGP (self-accelerating branch
of the Dvali-Gavadadze-Porrati braneworld gravity) model and the galileon
modified gravity model on the basis of the static and spherically symmetric
solutions of the collisionless Boltzmann equation, which reduce to the singular
isothermal sphere model and the King model in the limit of Newtonian gravity.
The common feature of these halos is that the density of a halo in the outer
region is larger (smaller) in the sDGP (galileon) model, respectively, in
comparison with Newtonian gravity. This comes from the suppression
(enhancement) of the effective gravity at large distance in the sDGP (galileon)
model, respectively. However, the difference between these modified gravity
models and Newtonian gravity only appears outside the halo due to the
Vainshtein mechanism, which makes it difficult to distinguish between them. We
also discuss the case in which the halo density profile is fixed independently
of the gravity model for comparison between our results and previous work.Comment: 15pages, 6 figures, maches the version to be published in Int. J.
Mod. Phys. D, typos correcte