46 research outputs found
Machine-learning interpolation of population-synthesis simulations to interpret gravitational-wave observations: A case study
We report on advances to interpret current and future gravitational-wave
events in light of astrophysical simulations. A machine-learning emulator is
trained on numerical population-synthesis predictions and inserted into a
Bayesian hierarchical framework. In this case study, a modest but
state-of-the-art suite of simulations of isolated binary stars is interpolated
across two event parameters and one population parameter. The validation
process of our pipelines highlights how omitting some of the event parameters
might cause errors in estimating selection effects, which propagates as
systematics to the final population inference. Using LIGO/Virgo data from O1
and O2 we infer that black holes in binaries are most likely to receive natal
kicks with one-dimensional velocity dispersion = 105+44 km/s. Our
results showcase potential applications of machine-learning tools in
conjunction with population-synthesis simulations and gravitational-wave data.Comment: 6 pages, 3 figure
Precise LIGO Lensing Rate Predictions for Binary Black Holes
We show how LIGO is expected to detect coalescing binary black holes at
, that are lensed by the intervening galaxy population. Gravitational
magnification, , strengthens gravitational wave signals by ,
without altering their frequencies, which if unrecognised leads to an
underestimate of the event redshift and hence an overestimate of the binary
mass. High magnifications can be reached for coalescing binaries because the
region of intense gravitational wave emission during coalescence is so small
(100km), permitting very close projections between lensing caustics and
gravitational-wave events. Our simulations incorporate accurate waveforms
convolved with the LIGO power spectral density. Importantly, we include the
detection dependence on sky position and orbital orientation, which for the
LIGO configuration translates into a wide spread in observed redshifts and
chirp masses. Currently we estimate a detectable rate of lensed events
\rateEarly{}, that rises to \rateDesign{}, at LIGO's design sensitivity limit,
depending on the high redshift rate of black hole coalescence.Comment: 5 pages, 4 figure
Distinguishing double neutron star from neutron star-black hole binary populations with gravitational wave observations
Gravitational waves from the merger of two neutron stars cannot be easily
distinguished from those produced by a comparable-mass mixed binary in which
one of the companions is a black hole. Low-mass black holes are interesting
because they could form in the aftermath of the coalescence of two neutron
stars, from the collapse of massive stars, from matter overdensities in the
primordial Universe, or as the outcome of the interaction between neutron stars
and dark matter. Gravitational waves carry the imprint of the internal
composition of neutron stars via the so-called tidal deformability parameter,
which depends on the stellar equation of state and is equal to zero for black
holes. We present a new data analysis strategy powered by Bayesian inference
and machine learning to identify mixed binaries, hence low-mass black holes,
using the distribution of the tidal deformability parameter inferred from
gravitational-wave observations.Comment: 13 pages, 6 figures - v2: matches the published version in Phys. Rev.
D 102, 02302
Multiband gravitational-wave event rates and stellar physics
Joint gravitational-wave detections of stellar-mass black-hole binaries by
ground- and space-based observatories will provide unprecedented opportunities
for fundamental physics and astronomy. We present a semianalytic method to
estimate multiband event rates by combining selection effects of ground-based
interferometers (like LIGO/Virgo) and space missions (like LISA). We forecast
the expected number of multiband detections first by using information from
current LIGO/Virgo data, and then through population synthesis simulations of
binary stars. We estimate that few to tens of LISA detections can be used to
predict mergers detectable on the ground. Conversely, hundreds of events could
potentially be extracted from the LISA data stream using prior information from
ground detections. In general, the merger signal of binaries observable by LISA
is strong enough to be unambiguously identified by both current and future
ground-based detectors. Therefore third-generation detectors will not increase
the number of multiband detections compared to LIGO/Virgo. We use population
synthesis simulations of isolated binary stars to explore some of the stellar
physics that could be constrained with multiband events, and we show that
specific formation pathways might be overrepresented in multiband events
compared to ground-only detections.Comment: 17 pages, 11 figures. Database and python code available at
https://github.com/dgerosa/spops - Published in PR