Shrobana Ghosh

Ultralight bosons can induce superradiant instabilities in spinning black holes, tapping their rotational energy to trigger the growth of a bosonic condensate. Possible observational imprints of these boson clouds include (i) direct detection of the nearly monochromatic (resolvable or stochastic) gravitational waves emitted by the condensate, and (ii) statistically significant evidence for the formation of ``holes'' at large spins in the spin versus mass plane (sometimes also referred to as ``Regge plane'') of astrophysical black holes. In this work, we focus on the prospects of LISA and LIGO detecting or constraining scalars with mass in the range ${m}_{s}\ensuremath{\in}[{10}^{\ensuremath{-}19},{10}^{\ensuremath{-}15}]\text{ }\text{ }\mathrm{eV}$ and ${m}_{s}\ensuremath{\in}[{10}^{\ensuremath{-}14},{10}^{\ensuremath{-}11}]\text{ }\text{ }\mathrm{eV}$, respectively. Using astrophysical models of black-hole populations calibrated to observations and black-hole perturbation theory calculations of the gravitational emission, we find that, in optimistic scenarios, LIGO could observe a stochastic background of gravitational radiation in the range ${m}_{s}\ensuremath{\in}[2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13},{10}^{\ensuremath{-}12}]\text{ }\text{ }\mathrm{eV}$, and up to $1{0}^{4}$ resolvable events in a 4-year search if ${m}_{s}\ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}\text{ }\text{ }\mathrm{eV}$. LISA could observe a stochastic background for boson masses in the range ${m}_{s}\ensuremath{\in}[5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}19},5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}]$, and up to $\ensuremath{\sim}{10}^{3}$ resolvable events in a 4-year search if ${m}_{s}\ensuremath{\sim}{10}^{\ensuremath{-}17}\text{ }\text{ }\mathrm{eV}$. LISA could further measure spins for black-hole binaries with component masses in the range $[{10}^{3},{10}^{7}]{M}_{\ensuremath{\bigodot}}$, which is not probed by traditional spin-measurement techniques. A statistical analysis of the spin distribution of these binaries could either rule out scalar fields in the mass range $\ensuremath{\sim}[4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18},{10}^{\ensuremath{-}14}]\text{ }\text{ }\mathrm{eV}$, or measure ${m}_{s}$ with ten percent accuracy if light scalars in the mass range $\ensuremath{\sim}[{10}^{\ensuremath{-}17},{10}^{\ensuremath{-}13}]\text{ }\text{ }\mathrm{eV}$ exist.

In this work we introduce phenomxo4a, the first phenomenological, frequency-domain gravitational waveform model to incorporate multipole asymmetries and precession angles tuned to numerical relativity. We build upon the modeling work that produced the phenompnr model and incorporate our additions into the imrphenomx framework, retuning the coprecessing frame model and extending the tuned precession angles to higher signal multipoles. We also include, for the first time in frequency-domain models, a recent model for spin-precession-induced multipolar asymmetry in the coprecessing frame to the dominant gravitational-wave multipoles. The accuracy of the full model and its constituent components is assessed through comparison to numerical relativity and numerical relativity surrogate waveforms by computing mismatches and performing parameter estimation studies. We show that, for the dominant signal multipole, we retain the modeling improvements seen in the phenompnr model. We find that the relative accuracy of current full IMR models varies depending on location in parameter space and the comparison metric, and on average they are of comparable accuracy. However, we find that variations in the pointwise accuracy do not necessarily translate into large biases in the parameter estimation recoveries.

Superradiant instabilities can trigger the formation of bosonic clouds around rotating black holes. If the bosonic field growth is sufficiently fast, these clouds could form shortly after a binary black hole merger. Such clouds are continuous sources of gravitational waves whose detection (or lack thereof) can probe the existence of ultralight bosons (such as axionlike particles) and their properties. Motivated by the binary black hole mergers seen by Advanced LIGO so far, we investigate in detail the parameter space that can be probed with continuous gravitational wave signals from ultralight scalar field clouds around black hole merger remnants with particular focus on future ground-based detectors (A+, Voyager and Cosmic Explorer). We also study the impact that the confusion noise from a putative stochastic gravitational-wave background from unresolved sources would have on such searches and we estimate, under different astrophysical priors, the number of binary black hole merger events that could lead to an observable postmerger signal. Under our most optimistic assumptions, Cosmic Explorer could detect dozens of postmerger signals.

We present a public catalog of numerical-relativity binary-black-hole simulations. The catalog contains datasets from 80 distinct configurations of precessing binary-black-hole systems, with mass ratios up to <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi>m</a:mi><a:mn>2</a:mn></a:msub><a:mo>/</a:mo><a:msub><a:mi>m</a:mi><a:mn>1</a:mn></a:msub><a:mo>=</a:mo><a:mn>8</a:mn></a:math>, dimensionless spin magnitudes on the larger black hole up to <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mo stretchy="false">|</c:mo><c:msub><c:mover accent="true"><c:mi>S</c:mi><c:mo stretchy="false">→</c:mo></c:mover><c:mn>2</c:mn></c:msub><c:mo stretchy="false">|</c:mo><c:mo>/</c:mo><c:msubsup><c:mi>m</c:mi><c:mn>2</c:mn><c:mn>2</c:mn></c:msubsup><c:mo>=</c:mo><c:mn>0.8</c:mn></c:math> (the small black hole is nonspinning), and a range of five values of spin misalignment for each mass-ratio/spin combination. We discuss the physical properties of the configurations in our catalog, and assess the accuracy of the initial configuration of each simulation and of the gravitational waveforms. We perform a careful analysis of the errors due to the finite resolution of our simulations and the finite distance from the source at which we extract the waveform data and provide a conservative estimate of the mismatch accuracy. We find that the upper limit on the mismatch uncertainty of our waveforms (including multipoles <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mo>ℓ</i:mo><i:mo>≤</i:mo><i:mn>5</i:mn></i:math>) is 0.4%. In doing this we present a consistent approach to combining mismatch uncertainties from multiple error sources. We compare this release to previous catalogs and discuss how these new simulations complement the existing public datasets. In particular, this is the first catalog to uniformly cover this parameter space of single-spin binaries and there was previously only sparse coverage of the precessing-binary parameter space for mass ratios <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mo>≳</k:mo><k:mn>5</k:mn></k:math>. We discuss applications of these new data, and the most urgent directions for future simulation work. Published by the American Physical Society 2024

Gravitational-wave signals from binaries that contain spinning black holes in general include an asymmetry between the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mo>+</a:mo><a:mi>m</a:mi></a:math> and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mo>−</c:mo><c:mi>m</c:mi></c:math> multipoles that is not included in most signal models used in LIGO-Virgo-KAGRA analysis to date. This asymmetry manifests itself in out-of-plane recoil of the final black hole and its inclusion in signal models is necessary both to measure this recoil, but also to accurately measure the full spin information of each black hole. We present the first model of the antisymmetric contribution to the dominant coprecessing-frame signal multipole throughout inspiral, merger, and ringdown. We model the antisymmetric contribution in the frequency domain, and take advantage of the approximations that the antisymmetric amplitude can be modeled as a ratio of the (already modeled) symmetric amplitude, and analytic relationships between the symmetric and antisymmetric phases during the inspiral and ringdown. The model is tuned to single-spin numerical-relativity simulations up to mass-ratio 8 and spin magnitudes of 0.8, and has been implemented in a recent phenomenological model for use in the fourth LIGO-Virgo-KAGRA observing run. However, the procedure described here can be easily applied to other time- or frequency-domain models. Published by the American Physical Society 2024