51 research outputs found
Global Stellar Budget for LIGO Black Holes
The binary black hole mergers observed by LIGO-Virgo gravitational-wave
detectors pose two major challenges: (i) how to produce these massive black
holes from stellar processes; and (ii) how to bring them close enough to merge
within the age of the universe? We derive a fundamental constraint relating the
binary separation and the available stellar budget in the universe to produce
the observed black hole mergers. We find that of the entire
budget contributes to the observed merger rate of
black holes, if the separation is around the diameter of their progenitor
stars. Furthermore, the upgraded LIGO detector and third-generation
gravitational-wave detectors are not expected to find stellar-mass black hole
mergers at high redshifts. From LIGO's strong constraints on the mergers of
black holes in the pair-instability mass-gap (), we
find that of all massive stars contribute to a remnant black
hole population in this gap. Our derived separationbudget constraint
provides a robust framework for testing the formation scenarios of stellar
binary black holes
Pointing LISA-like gravitational wave detectors
Space-based gravitational wave detectors based on the Laser Interferometer
Space Antenna (LISA) design operate by synthesizing one or more interferometers
from fringe velocity measurements generated by changes in the light travel time
between three spacecraft in a special set of drag-free heliocentric orbits.
These orbits determine the inclination of the synthesized interferometer with
respect to the ecliptic plane. Once these spacecraft are placed in their
orbits, the orientation of the interferometers at any future time is fixed by
Kepler's Laws based on the initial orientation of the spacecraft constellation,
which may be freely chosen. Over the course of a full solar orbit, the initial
orientation determines a set of locations on the sky were the detector has
greatest sensitivity to gravitational waves as well as a set of locations where
nulls in the detector response fall. By artful choice of the initial
orientation, we can choose to optimize or suppress the antennas sensitivity to
sources whose location may be known in advance (e.g., the Galactic Center or
globular clusters).Comment: 24 pages, 7 figures, submitted to Ap
Detectability of Intermediate-Mass Black Holes in Multiband Gravitational Wave Astronomy
The direct measurement of gravitational waves is a powerful tool for
surveying the population of black holes across the universe. The first
gravitational wave catalog from LIGO has detected black holes as heavy as
, colliding when our Universe was about half its current age.
However, there is yet no unambiguous evidence of black holes in the
intermediate-mass range of . Recent electromagnetic
observations have hinted at the existence of IMBHs in the local universe;
however, their masses are poorly constrained. The likely formation mechanisms
of IMBHs are also not understood. Here we make the case that multiband
gravitational wave astronomy --specifically, joint observations by space- and
ground-based gravitational wave detectors-- will be able to survey a broad
population of IMBHs at cosmological distances. By utilizing general
relativistic simulations of merging black holes and state-of-the-art
gravitational waveform models, we classify three distinct population of
binaries with IMBHs in the multiband era and discuss what can be observed about
each. Our studies show that multiband observations involving the upgraded LIGO
detector and the proposed space-mission LISA would detect the inspiral, merger
and ringdown of IMBH binaries out to redshift ~2. Assuming that next-generation
detectors, Einstein Telescope, and Cosmic Explorer, are operational during
LISA's mission lifetime, we should have multiband detections of IMBH binaries
out to redshift ~5. To facilitate studies on multiband IMBH sources, here we
investigate the multiband detectability of IMBH binaries. We provide analytic
relations for the maximum redshift of multiband detectability, as a function of
black hole mass, for various detector combinations. Our study paves the way for
future work on what can be learned from IMBH observations in the era of
multiband gravitational wave astronomy
Georgia Tech Catalog of Gravitational Waveforms
This paper introduces a catalog of gravitational waveforms from the bank of
simulations by the numerical relativity effort at Georgia Tech. Currently, the
catalog consists of 452 distinct waveforms from more than 600 binary black hole
simulations: 128 of the waveforms are from binaries with black hole spins
aligned with the orbital angular momentum, and 324 are from precessing binary
black hole systems. The waveforms from binaries with non-spinning black holes
have mass-ratios , and those with precessing, spinning
black holes have . The waveforms expand a moderate number of orbits in
the late inspiral, the burst during coalescence, and the ring-down of the final
black hole. Examples of waveforms in the catalog matched against the widely
used approximate models are presented. In addition, predictions of the mass and
spin of the final black hole by phenomenological fits are tested against the
results from the simulation bank. The role of the catalog in interpreting the
GW150914 event and future massive binary black-hole search in LIGO is
discussed. The Georgia Tech catalog is publicly available at
einstein.gatech.edu/catalog
Coping with Junk Radiation in Binary Black Hole Simulations
Spurious junk radiation in the initial data for binary black hole numerical
simulations has been an issue of concern. The radiation affects the masses and
spins of the black holes, modifying their orbital dynamics and thus potentially
compromising the accuracy of templates used in gravitational wave analysis. Our
study finds that junk radiation effects are localized to the vicinity of the
black holes. Using insights from single black hole simulations, we obtain
fitting formulas to estimate the changes from junk radiation on the mass and
spin magnitude of the black holes in binary systems. We demonstrate how these
fitting formulas could be used to adjust the initial masses and spin magnitudes
of the black holes, so the resulting binary has the desired parameters after
the junk radiation has left the computational domain. A comparison of waveforms
from raw simulations with those from simulations that have been adjusted for
junk radiation demonstrate that junk radiation could have an appreciable effect
on the templates for LIGO sources with SNRs above 30.Comment: 5 pages, 6 figure
Inferring Parameters of GW170502: The Loudest Intermediate-mass Black Hole Trigger in LIGO's O1/O2 data
Gravitational wave (GW) measurements provide the most robust constraints of
the mass of astrophysical black holes. Using state-of-the-art GW signal models
and a unique parameter estimation technique, we infer the source parameters of
the loudest marginal trigger, GW170502, found by LIGO from 2015 to 2017. If
this trigger is assumed to be a binary black hole merger, we find it
corresponds to a total mass in the source frame of
at redshift . The
primary and secondary black hole masses are constrained to
and
respectively, with 90\% confidence. Across all signal models, we find probability for the effective spin parameter .
Furthermore, we find that the inclusion of higher-order modes in the analysis
narrows the confidence region for the primary black hole mass by 10\%, however,
the evidence for these modes in the data remains negligible. The techniques
outlined in this study could lead to robust inference of the physical
parameters for all intermediate-mass black hole binary candidates
in the current GW network.Comment: 6 pages, 4 figures, 3 tables; Accepted for publication in the
Astrophysical Journa
Targeted numerical simulations of binary black holes for GW170104
In response to LIGO's observation of GW170104, we performed a series of full
numerical simulations of binary black holes, each designed to replicate likely
realizations of its dynamics and radiation. These simulations have been
performed at multiple resolutions and with two independent techniques to solve
Einstein's equations. For the nonprecessing and precessing simulations, we
demonstrate the two techniques agree mode by mode, at a precision substantially
in excess of statistical uncertainties in current LIGO's observations.
Conversely, we demonstrate our full numerical solutions contain information
which is not accurately captured with the approximate phenomenological models
commonly used to infer compact binary parameters. To quantify the impact of
these differences on parameter inference for GW170104 specifically, we compare
the predictions of our simulations and these approximate models to LIGO's
observations of GW170104.Comment: 11 figures, 20 page
A Parameter Estimation Method that Directly Compares Gravitational Wave Observations to Numerical Relativity
We present and assess a Bayesian method to interpret gravitational wave
signals from binary black holes. Our method directly compares gravitational
wave data to numerical relativity simulations. This procedure bypasses
approximations used in semi-analytical models for compact binary coalescence.
In this work, we use only the full posterior parameter distribution for generic
nonprecessing binaries, drawing inferences away from the set of NR simulations
used, via interpolation of a single scalar quantity (the marginalized
log-likelihood, ) evaluated by comparing data to nonprecessing
binary black hole simulations. We also compare the data to generic simulations,
and discuss the effectiveness of this procedure for generic sources. We
specifically assess the impact of higher order modes, repeating our
interpretation with both as well as harmonic modes. Using the
higher modes, we gain more information from the signal and can better
constrain the parameters of the gravitational wave signal. We assess and
quantify several sources of systematic error that our procedure could
introduce, including simulation resolution and duration; most are negligible.
We show through examples that our method can recover the parameters for equal
mass, zero spin; GW150914-like; and unequal mass, precessing spin sources. Our
study of this new parameter estimation method demonstrates we can quantify and
understand the systematic and statistical error. This method allows us to use
higher order modes from numerical relativity simulations to better constrain
the black hole binary parameters.Comment: 30 pages, 22 figures; submitted to PR
What we can learn from multi-band observations of black hole binaries
The LIGO/Virgo gravitational-wave (GW) interferometers have to-date detected ten merging black hole (BH) binaries, some with masses considerably larger than had been anticipated. Stellar-mass BH binaries at the high end of the observed mass range (with "chirp mass" M ≳ 25M⊙) should be detectable by a space-based GW observatory years before those binaries become visible to ground-based GW detectors. This white paper discusses some of the synergies that result when the same binaries are observed by instruments in space and on the ground. We consider intermediate-mass black hole binaries (with total mass M∼10²−10⁴ M⊙) as well as stellar-mass black hole binaries. We illustrate how combining space-based and ground-based data sets can break degeneracies and thereby improve our understanding of the binary's physical parameters. While early work focused on how space-based observatories can forecast precisely when some mergers will be observed on the ground, the reverse is also important: ground-based detections will allow us to "dig deeper" into archived, space-based data to confidently identify black hole inspirals whose signal-to-noise ratios were originally sub-threshold, increasing the number of binaries observed in both bands by a factor of ∼4−7
Snowmass2021 Cosmic Frontier White Paper: Future Gravitational-Wave Detector Facilities
The next generation of gravitational-wave observatories can explore a wide
range of fundamental physics phenomena throughout the history of the universe.
These phenomena include access to the universe's binary black hole population
throughout cosmic time, to the universe's expansion history independent of the
cosmic distance ladders, to stochastic gravitational-waves from early-universe
phase transitions, to warped space-time in the strong-field and high-velocity
limit, to the equation of state of nuclear matter at neutron star and
post-merger densities, and to dark matter candidates through their interaction
in extreme astrophysical environments or their interaction with the detector
itself. We present the gravitational-wave detector concepts than can drive the
future of gravitational-wave astrophysics. We summarize the status of the
necessary technology, and the research needed to be able to build these
observatories in the 2030s.Comment: 31 pages, 5 figures, contribution to Snowmass 202
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