arXiv subjects

Lorenzo Mirasola

Publications and source records attributed to Lorenzo Mirasola.

6 recordsLinked to original sources

arXiv2026

Search for Long-Transient Gravitational Waves from Supernova SN2023ixf using GFH-v2 Pipeline

We present a directed search for long-transient gravitational waves from the possible newborn magnetar remnant of SN2023ixf, a nearby Type II core-collapse supernova in the M101 galaxy. The analysis uses LIGO Hanford and Livingston data from Engineering Run 15, using coincident data lying within the on-source window associated with the supernova. We target signals from a rapidly rotating, non-axisymmetric neutron star whose spin-down is dominated by gravitational-wave emission, producing a power-law decrease in frequency and a corresponding decrease in strain amplitude. The search is performed with the GFH-v2 pipeline, based on the Generalized Frequency Hough transform. No candidate survives the coincidence and follow-up analysis. We therefore set upper limits on the maximum detectable distance as a function of initial frequency and ellipticity. For the highest ellipticity interval, the 90% upper limits reach distances of about 1-2.5~Mpc across most of the analysed band. Although these limits are below the distance to M101, the search provides the first application of GFH-v2 to a nearby core-collapse supernova and characterizes its performance on real detector data.

astro-ph.IM↗

arXiv2026

Impact of coalescence signals on the search for continuous gravitational waves with Einstein Telescope

The current network of gravitational wave detectors has already revealed hundreds of compact binary coalescences (CBCs), including binary neutron stars, binary black holes, and black hole-neutron star systems. As detector sensitivity improves, the superposition of these signals is expected to form an astrophysical background that becomes increasingly relevant for future observatories. In third generation detectors, such as the Einstein Telescope (ET), this background will be most prominent at low frequencies, potentially affecting the search for continuous gravitational waves (CWs) from spinning neutron stars. In this work, we evaluate the impact of the CBC background on CW detection using the Frequency-Hough pipeline, with a focus on the low-frequency performance in ET sensitivity conditions. Through realistic simulations of the unresolved CBC background, we find that it acts as an additional noise source, most strongly affecting the detection of CW signals around 7 Hz, worsening the FH sensitivity by about 7-10%.

gr-qc↗

arXiv2026

py5vec: a modular Python package for the 5-vector method to search for continuous gravitational waves

We present \texttt{py5vec}, a Python package for implementing and extending the 5-vector method, used to search for continuous gravitational wave (CW) signals. We also provide a comprehensive theoretical review of the 5-vector method and extend the relative likelihood formalism by marginalizing over the noise variance, resulting in a more robust Student's t-likelihood, and over the initial phase to account for pulsar glitches. \texttt{py5vec} provides a modular architecture that separates data representation, signal demodulation, and statistical inference into independent abstract stages. It supports multiple input data formats and interoperates with existing Python software, providing a bridge between different approaches. For example, using a \texttt{bilby}-based interface, \texttt{py5vec} implements Bayesian parameter estimation within the 5-vector formalism for the first time. The modular design also allows for making exact multi-level and direct comparisons between other software, such as \texttt{cwinpy} and \texttt{SNAG} in MATLAB. In \texttt{py5vec}, we implement a multidetector targeted search for known pulsars, validated using LIGO data from the O4a run and hardware injections, demonstrating consistent reconstruction of signal parameters. This package therefore provides a flexible platform for current targeted searches and for future extensions to other CW search strategies.

astro-ph.IM↗

arXiv2025

Search for continuous gravitational wave signals from luminous dark photon superradiance clouds with LVK O3 observations

Superradiance clouds of kinetically-mixed dark photons around spinning black holes can produce observable multi-messenger electromagnetic and gravitational wave signals. The cloud generates electric fields of up to a Teravolt-per-meter, which lead to a cascade production of charged particles, yielding a turbulent quasi-equilibrium plasma around the black hole, and resulting in electromagnetic fluxes ranging from supernova to pulsar-like luminosities. For stellar mass black holes, such systems resemble millisecond pulsars and are expected to emit pulsating radio waves and continuous gravitational waves (CWs) within the LIGO-Virgo-KAGRA (LVK) sensitivity band. We select 44 sources with approximately coincident frequencies or positive frequency drifts from existing pulsar catalogs as potential candidates of long-lasting superradiance clouds around old galactic black holes. For a subset of 34 sources that are well measured and have not been previously targeted, we perform the first search for CW emission in LVK data from the third observing run. We find no evidence of a CW signal and place 95% confidence level upper limits on the emitted strain amplitude. We interpret these results, together with limits from previous searches, in terms of the underlying dark photon theory by performing an analysis of the expected signals from superradiance clouds from galactic black holes. We find that, even for moderately spinning black holes, the absence of an observed CW signal disfavors a discrete set of dark photon masses between about $10^{-13}$ $\rm{eV}/c^2$ and $10^{-12}$ $\rm{eV}/c^2$ and kinetic mixing couplings in the range of $10^{-9}$-$10^{-7}$, subject to assumptions about the properties of the black hole population and the cloud's electromagnetic emission.

gr-qc↗

arXiv2025

Toward a computationally-efficient follow-up pipeline for blind continuous gravitational-wave searches

The sensitivity of continuous gravitational-wave (CW) searches for unknown neutron stars (NSs) is limited by their parameter space breadth. To fit within reasonable computing budgets, hierarchical schemes are used to identify interesting candidates using affordable methods. The resulting sensitivity depends on the number of candidates selected to follow-up. In this work, we present a novel framework to evaluate the effectiveness of stochastic CW follow-ups. Our results allow for a significant reduction of the computing cost of pyfstat, a well-established follow-up method. We also simplify the setup of multistage follow-ups by removing the need for parameter-space metrics. The study was conducted on Gaussian and real O3 Advanced LIGO data covering both isolated and binary sources. These results will have a positive impact on the sensitivity of all-sky searches in the forthcoming observing runs of the LIGO-Virgo-KAGRA collaboration.

gr-qc↗

arXiv2024

New semicoherent targeted search for continuous gravitational waves from pulsars in binary systems

We present a novel semicoherent targeted search method for continuous gravitational waves (CWs) emitted by pulsars in binary systems. The method is based on a custom optimization of the coherence time, which is tailored according to the orbital parameters and their uncertainties, as provided by electromagnetic observations. While rotating pulsars are expected to produce quasimonochromatic CWs in their reference frame, their orbital motion introduces additional modulation in the observer's frame, alongside the modulation caused by the Earth's motion. As a result, the received signal is spread across a frequency range, and demodulation techniques must be used to improve sensitivity. However, Doppler corrections can, in some cases, vary significantly within the uncertainties of the orbital parameters, potentially lowering the detection chances of single-template, fully coherent searches. To exploit the constraints derived from electromagnetic observations, we implement a semicoherent search that is more robust than other methods. In this approach, the coherence time is evaluated for each source, taking into account the uncertainties in its orbital parameters. This method was tested and applied to a set of thirteen targets from the ATNF catalog. The search identified one outlier, whose astrophysical origin has been confidently excluded. For the first time to our knowledge, we then set upper limits on the signal strain from these 12 pulsars, with the lowest limit being $h_{UL}\sim9.01\times 10^{-26}$ for PSR~J1326-4728B.

gr-qc↗