arXiv subjects

F. Pannarale

Publications and source records attributed to F. Pannarale.

6 recordsLinked to original sources

arXiv2025

3+1 GRHD simulations of NSBH mergers with light black holes using public codes

Recent observations of compact binary systems have provided evidence for black holes with masses below standard expectations. When paired with neutron stars (NSs), such low-mass black holes (BHs) have the potential to be detected by future multimessenger campaigns and could unveil unknown features of the BH population in the universe. Given the importance of accurate models for matched-filtering searches and Bayesian parameter estimation in discoveries of this sort, attention has renewed on the limitations of low-mass NSBH merger models and on the downstream impact of such limitations on gravitational-wave data analysis. Previous numerical relativity (NR) studies have revealed discrepancies in the predicted merger time, as well as more general mismatches and dephasing between phenomenological models and high-resolution simulations. The simulation presented here was motivated by these findings and illustrates how publicly available tools can be applied to this specific science case, towards informing next-generation, more refined gravitational-wave and kilonovae models. Here, we summarize the setup of a high-resolution general relativistic hydrodynamics simulation of an equal-mass NSBH system performed entirely with public codes (Einstein Toolkit and FUKA) and a finite-temperature equation of state. The results we show include the $(\ell,m)=(2,2)$ strain and 2D snapshots of the system undergoing tidal disruption and early postmerger disk formation. The system evolved for $\sim 4$ orbits while the $L_2$ norm of the Hamiltonian constraint remained below $6\times10^{-7}$ throughout the inspiral prior to growing near merger time.

gr-qc↗

arXiv2016

Validating gravitational-wave detections: The Advanced LIGO hardware injection system

Hardware injections are simulated gravitational-wave signals added to the Laser Interferometer Gravitational-wave Observatory (LIGO). The detectors' test masses are physically displaced by an actuator in order to simulate the effects of a gravitational wave. The simulated signal initiates a control-system response which mimics that of a true gravitational wave. This provides an end-to-end test of LIGO's ability to observe gravitational waves. The gravitational-wave analyses used to detect and characterize signals are exercised with hardware injections. By looking for discrepancies between the injected and recovered signals, we are able to characterize the performance of analyses and the coupling of instrumental subsystems to the detectors' output channels. This paper describes the hardware injection system and the recovery of injected signals representing binary black hole mergers, a stochastic gravitational wave background, spinning neutron stars, and sine-Gaussians.

astro-ph.IM↗

arXiv2015

Double Compact Objects III: Gravitational Wave Detection Rates

The unprecedented range of second-generation gravitational-wave (GW) observatories calls for refining the predictions of potential sources and detection rates. The coalescence of double compact objects (DCOs)---i.e., neutron star-neutron star (NS-NS), black hole-neutron star (BH-NS), and black hole-black hole (BH-BH) binary systems---is the most promising source of GWs for these detectors. We compute detection rates of coalescing DCOs in second-generation GW detectors using the latest models for their cosmological evolution, and implementing inspiral-merger-ringdown (IMR) gravitational waveform models in our signal-to-noise ratio calculations. We find that: (1) the inclusion of the merger/ringdown portion of the signal does not significantly affect rates for NS-NS and BH-NS systems, but it boosts rates by a factor $\sim 1.5$ for BH-BH systems; (2) in almost all of our models BH-BH systems yield by far the largest rates, followed by NS-NS and BH-NS systems, respectively, and (3) a majority of the detectable BH-BH systems were formed in the early Universe in low-metallicity environments. We make predictions for the distributions of detected binaries and discuss what the first GW detections will teach us about the astrophysics underlying binary formation and evolution.

astro-ph.HE↗

arXiv2012

On the validity of the adiabatic approximation in compact binary inspirals

Using a semi-analytical approach recently developed to model the tidal deformations of neutron stars in inspiralling compact binaries, we study the dynamical evolution of the tidal tensor, which we explicitly derive at second post-Newtonian order, and of the quadrupole tensor. Since we do not assume a priori that the quadrupole tensor is proportional to the tidal tensor, i.e. the so called "adiabatic approximation", our approach enables us to establish to which extent such approximation is reliable. We find that the ratio between the quadrupole and tidal tensors (i.e., the Love number) increases as the inspiral progresses, but this phenomenon only marginally affects the emitted gravitational waveform. We estimate the frequency range in which the tidal component of the gravitational signal is well described using the stationary phase approximation at next-to-leading post-Newtonian order, comparing different contributions to the tidal phase. We also derive a semi-analytical expression for the Love number, which reproduces within a few percentage points the results obtained so far by numerical integrations of the relativistic equations of stellar perturbations.

gr-qc↗

arXiv2010

A Semi-relativistic Model for Tidal Interactions in BH-NS Coalescing Binaries

We study the tidal effects of a Kerr black hole on a neutron star in black hole-neutron star binary systems using a semi-analytical approach which describes the neutron star as a deformable ellipsoid. Relativistic effects on the neutron star self-gravity are taken into account by employing a scalar potential resulting from relativistic stellar structure equations. We calculate quasi-equilibrium sequences of black hole-neutron star binaries, and the critical orbital separation at which the star is disrupted by the black hole tidal field: the latter quantity is of particular interest because when it is greater than the radius of the innermost stable circular orbit, a short gamma-ray burst scenario may develop.

astro-ph↗

arXiv2010

Neutron star tidal disruption in mixed binaries: the imprint of the equation of state

We study the tidal disruption of neutron stars in black hole-neutron star coalescing binaries. We calculate the critical orbital separation at which the star is disrupted by the black hole tidal field for several equations of state describing the matter inside the neutron star, and for a large set of the binary parameters. When the disruption occurs before the star reaches the innermost stable circular orbit, the gravitational wave (GW) signal emitted by the system is expected to exhibit a cutoff frequency nu_GWtide, which is a distinctive feature of the waveform. We evaluate nu_GWtide and show that, if this frequency will be found in a detected gravitational wave, it will allow to determine the neutron star radius with an error of a few percent, providing valuable information on the behaviour of matter in the stellar core.

gr-qc↗