arXiv subjects

A. Królak

Publications and source records attributed to A. Królak.

4 recordsLinked to original sources

arXiv2025

Pattern-recognition techniques to search for gravitational waves from inspiraling, dark-dressed primordial black holes

Primordial black holes (PBHs) are compelling dark matter (DM) candidates, but current constraints suggest they cannot compose all of DM. This implies that additional DM components could coexist with PBHs, one of which could form "dark dresses" (DDs) around PBHs. DDs would cause PBH binaries to experience dynamical friction (DF), which would accelerate their inspirals with respect to those in vacuum. Ignoring DF effects in matched-filtering searches could lead to significant sensitivity loss, especially in systems with asymmetric mass-ratios of q ~ 10^{-3}. We thus show that a method designed to find time-frequency power-law tracks from inspiraling PBHs in vacuum could actually handle the presence of DDs with minimal modifications. This method, the generalized frequency-Hough (GFH), maps points in the detector's time-frequency plane to lines in the source parameter space. We show that this pattern-recognition technique can recover simulated DD signals in Gaussian noise, marking an important step forward in developing DM-aware methods beyond matched filtering.

gr-qc↗

arXiv2014

Reconstruction of the gravitational wave signal $h(t)$ during the Virgo science runs and independent validation with a photon calibrator

The Virgo detector is a kilometer-scale interferometer for gravitational wave detection located near Pisa (Italy). About 13 months of data were accumulated during four science runs (VSR1, VSR2, VSR3 and VSR4) between May 2007 and September 2011, with increasing sensitivity. In this paper, the method used to reconstruct, in the range 10 Hz-10 kHz, the gravitational wave strain time series $h(t)$ from the detector signals is described. The standard consistency checks of the reconstruction are discussed and used to estimate the systematic uncertainties of the $h(t)$ signal as a function of frequency. Finally, an independent setup, the photon calibrator, is described and used to validate the reconstructed $h(t)$ signal and the associated uncertainties. The uncertainties of the $h(t)$ time series are estimated to be 8% in amplitude. The uncertainty of the phase of $h(t)$ is 50 mrad at 10 Hz with a frequency dependence following a delay of 8 $μ$s at high frequency. A bias lower than $4\,\mathrm{μs}$ and depending on the sky direction of the GW is also present.

gr-qc↗

arXiv2014

Searching for gravitational waves from known pulsars at once and twice the spin frequency

The existence of a superfluid core in the interior of a rotating neutron star may have an influence on its gravitational wave emission. In addition to the usually-assumed pure quadrupole radiation with the gravitational wave frequency at twice the spin frequency, a frequency of rotation itself may also be present in the gravitational wave spectrum. We study the parameters of a general model for such emission, compare it with previously proposed, simpler models, discuss the feasibility of the recovery of the stellar parameters and carry out the Monte Carlo simulations to test the performance of our estimation method.

gr-qc↗

arXiv2008

All-sky search of NAUTILUS data

A search for periodic gravitational-wave signals from isolated neutron stars in the NAUTILUS detector data is presented. We have analyzed half a year of data over the frequency band $<922.2; 923.2>$ Hz, the spindown range $<-1.463\times10^{-8}; 0>$ Hz/s and over the entire sky. We have divided the data into 2 day stretches and we have analyzed each stretch coherently using matched filtering. We have imposed a low threshold for the optimal detection statistic to obtain a set of candidates that are further examined for coincidences among various data stretches. For some candidates we have also investigated the change of the signal-to-noise ratio when we increase the observation time from two to four days. Our analysis has not revealed any gravitational-wave signals. Therefore we have imposed upper limits on the dimensionless gravitational-wave amplitude over the parameter space that we have searched. Depending on frequency, our upper limit ranges from $3.4 \times 10^{-23}$ to $1.3 \times 10^{-22}$. We have attempted a statistical verification of the hypotheses leading to our conclusions. We estimate that our upper limit is accurate to within 18%.

gr-qc↗