arXiv subjects

Alex Correia

Publications and source records attributed to Alex Correia.

4 recordsLinked to original sources

arXiv2025

Mining the Alerts: A Preliminary Catalog of Compact Binaries from the Fourth Observing Run

We present a preliminary catalog of compact binary merger candidates from the ongoing fourth observing run (O4) of Advanced LIGO, Virgo, and KAGRA, based on an analysis of public alerts distributed through GraceDB as of May 2025. We developed and applied methods to estimate the source-frame chirp mass for each candidate by utilizing information from public data products, including source classification probabilities, sky localizations, and observatory status. Combining our O4 analysis with previous catalogs, we provide updated estimates for the local merger rate density. For sources with chirp mass characteristic of binary neutron stars ($[1, 1.5]\,M_\odot$), we find a rate of $56^{+99}_{-40}$ $\textrm{Gpc}^{-3}\,\textrm{yr}^{-1}$. For systems in the expected neutron star--black hole chirp mass range ($[1.5, 3.5]\,M_\odot$), the rate is $36^{+32}_{-20}$ $\textrm{Gpc}^{-3}\,\textrm{yr}^{-1}$, and for heavier binary black holes ($[3.5, 100]\,M_\odot$), we estimate a rate of $19^{+4}_{-2}$ $\textrm{Gpc}^{-3}\,\textrm{yr}^{-1}$. This work provides an early glimpse into the compact binary population being observed in O4; we identify a number of high-value candidates up to signal-to-noise $\sim 80$, which we expect to enable precision measurements in the future.

astro-ph.HE↗

arXiv2025

Potential science with GW250114 -- the loudest binary black hole merger detected to date

On January 14, 2025 the LIGO interferometers detected a gravitational wave from the merger of two black holes, GW250114. Using publicly available information, we estimate that the signal-to-noise ratio (SNR) of GW250114 was $\sim 80$. This would make it three to four times louder than any other gravitational wave detected to date. GW250114 therefore offers a unique opportunity to make precise measurements of its source parameters and to test general relativity. In anticipation of its public data release, we analyze a set of simulated signals that have parameters similar to what we estimate for GW250114 and explore what new insights may be gained from this significant event. We investigate how well the component spins may be constrained, whether any eccentricity may be measured, what quasi-normal modes (QNMs) may be detected in the post-merger signal, how well the black hole area theorem may be constrained, and what constraints may be expected on sub-dominant inspiral-merger-ringdown modes. We find that it should be possible to measure a non-zero eccentricity at $20\,$Hz ($e_{20}$) if GW250114 has $e_{20} \gtrsim 0.05$. We also find that at least one overtone of the dominant QNM should be detectable in the ringdown of GW250114, with a Bayes factor of $O(10^3)$ after marginalizing over all timing uncertainties.

gr-qc↗

arXiv2024

Sky marginalization in black hole spectroscopy and tests of the area theorem

Direct observation of gravitational waves from binary black hole (BBH) mergers has made it possible to test the laws of black hole thermodynamics using real astrophysical sources. These tests rely on accurate and unbiased parameter estimates from the pre and postmerger portions of a signal. Due to numerical complications, previous analyses have fixed the sky location and coalescence time when independently estimating the parameters of the pre and postmerger signal. Here we overcome the numerical complications and present a novel method of marginalizing over sky location and coalescence time. Doing so, we find that it is not possible to model only the pre or postmerger portions of the signal while marginalizing over timing uncertainty. We surmount this problem by simultaneously yet independently modeling the pre and postmerger signal, with only the sky location and coalescence time being shared between the models. This allows us to marginalize over all parameters. We use our method to measure the change in area $ΔA_{\rm measured} = A_f - A_i$ between the final and initial black holes in the BBH merger GW150914. To measure the final black hole's area $A_f$ we do an analysis using quasinormal modes (QNMs) to model the postmerger signal, and another analysis using the postmerger portion of an inspiral-merger-ringdown (IMR) template. We find excellent agreement with expectations from general relativity. The Hawking area theorem (which states that $A_f \geq A_i$) is confirmed to $95.4\%$ and $99.5\%$ confidence using the QNM and IMR postmerger models, respectively. Both models yield $ΔA_{\rm measured} / ΔA_{\rm expected} \sim 1$, where $ΔA_{\rm expected}$ is the expected change in area derived from fits to numerical relativity simulations.

gr-qc↗

arXiv2023

Low evidence for ringdown overtone in GW150914 when marginalizing over time and sky location uncertainty

Tests of the no-hair theorem using astrophysical black holes involve the detection of at least two quasi-normal modes (QNMs) in the gravitational wave emitted by a perturbed black hole. A detection of two modes -- the dominant, $(\ell, m, n) = (2,2,0)$, mode and its first overtone, the $(2,2,1)$ mode -- in the post-merger signal of the binary black hole merger GW150914 was claimed in Isi et al. [arXiv:1905.00869], with further evidence provided in Isi & Farr [arXiv:2202.02941]. However, Cotesta et al. [arXiv:2201.00822] disputed this claim, finding that evidence for the overtone only appeared if the signal was analyzed before merger, when a QNM description of the signal is not valid. Due to technical challenges, both of these analyses fixed the merger time and sky location of GW150914 when estimating the evidence for the overtone. At least some of the contention can be attributed to fixing these parameters. Here, we surmount this difficulty and fully marginalize over merger time and sky-location uncertainty while doing a post-merger QNM analysis of GW150914. We find that marginalizing over all parameters yields low evidence for the presence of the overtone, with a Bayes factor of $1.10\pm 0.03$ in favor of a QNM model with the overtone versus one without. The arrival time uncertainty of GW150914 is too large to definitively claim detection of the $(2,2,1)$ mode.

gr-qc↗