arXiv subjects

Snehal Tibrewal

Publications and source records attributed to Snehal Tibrewal.

5 recordsLinked to original sources

arXiv2026

Impact of eccentricity and higher-modes on neutron star-black hole parameter estimation

Detections of gravitational waves from neutron star-black hole systems provide avenues for studying extreme matter, constraining binary formation channels, and testing the nature of compact objects in strong gravity. Eccentric signatures in the signal further enhance this potential by improving parameter estimation and offering clues about binary formation. Because eccentricity is primarily imprinted during the inspiral phase, it is often weakly constrained or missed entirely in binary black hole observations; in contrast, neutron star-black hole systems produce longer in-band signals, enabling more precise measurements of eccentricity and leaving a distinct imprint on parameter inference. In this work, we present a systematic parameter-estimation study exploring the impact of eccentricity on inference using injections simulated with the state-of-the-art eccentric waveform model SEOBNRv5EHM. We find that for systems like GW200105_162426, the measurement precision of eccentricity and correlated parameters improves as eccentricity increases, yielding tighter constraints at larger eccentricities. For the highest eccentricity considered in this study, $e=0.25$, we recover eccentricity with $1σ$ uncertainty as low as $4\times10^{-4}$. In addition, the constraints on effective spin $χ_\mathrm{eff}$ and mass ratio $q$ improve relative to the quasi-circular case by factors of $\sim13$ and $\sim20$, respectively. On the other hand, we find no significant improvement in extrinsic parameters such as luminosity distance and sky localization, suggesting that for systems like GW200105_162426, the additional information provided by eccentricity in this sector is either negligible or degenerate with the information provided by higher-order modes.

astro-ph.HE↗

arXiv2026

Eccentricity as a Magnifying Glass: Precision Population Inference Enabled by Eccentric Neutron Star-Black Hole Mergers

The formation history of compact binary systems remains one of the key open questions in astrophysics. Theoretical studies generally favor isolated binary evolution for neutron star-black hole (NSBH) systems, which tends to produce nearly circular orbits. However, recent analyses of the gravitational-wave event GW200105 indicate that its source has measurable eccentricity, suggesting that alternative formation channels may also contribute. It has been shown that the intrinsic parameters of eccentric NSBH mergers, such as the component masses and spins, are much better measured than circular mergers with LIGO-Virgo-KAGRA (LVK) observatories. We explore how such eccentricity-enhanced parameter measurements can affect the inference of NSBH formation channels. We find that sharper measurements of the effective spin parameter $χ_{\rm eff}$ increase the fraction of systems for which negative values can be confidently identified, allowing for the clear measurement of a spin-orbit misaligned event every $\sim 2.5$ eccentric NSBH detections for an isotropically distributed population in the fifth LVK observing run (O5). Improved NS mass measurements provide better constraining power for NS mass distributions, potentially revealing structure and tightening the bounds that can be drawn on their upper and lower masses. Similarly, the recovery of a metallicity-dependent BH mass distribution is improved by eccentricity-enhanced measurements. Finally, we show that the proposed population-level eccentricity distribution for dynamical-formation channels can be tested by the end of O5.

astro-ph.HE↗

arXiv2026

Misinterpreting Spin Precession as Orbital Eccentricity in Gravitational-Wave Signals

The increasing scope and breadth of gravitational wave detectors is providing the opportunity to explore new parameters in gravitational-wave astronomy. Eccentricity and spin-precession are two key observables to infer the origin of a gravitational wave (GW) source. The interpretation of GW source parameters can be plagued by degeneracy, such as the well-known degeneracy between mass and spin. As the field has explored new parameters, questions have been raised about possible degeneracies between eccentricity and spin-precession. Although some state-of-the-art models now include these effects individually, models that incorporate spin-precession and eccentricity are only in their infancy. Until models faithfully cover the complete parameter space of compact binary coalescence, our ability to correctly measure the source parameters and infer the formation of the binary is compromised. Here, we present a study of the distinguishability of these two key parameters. Our work finds that there is indeed a degeneracy between eccentricity and spin-precession; however, it is a highly localized effect. We find that the misidentified eccentricity estimates get worse as the signal gets shorter. Additionally, this misidentification is highly sensitive to the inclination angle of the source system. We provide quantifiable estimates of the potency of this degeneracy in addition to identifying some of the regions of parameter space where this degeneracy exists.

gr-qc↗

arXiv2025

Revisiting GW150914 with a non-planar, eccentric waveform model

The first direct detection of gravitational waves by the LIGO collaboration, GW150914, marked the start of a new exciting era in astronomy, enabling the study of the Universe through a new messenger. Since then, the field has grown rapidly, with the development of increasingly more sophisticated techniques to detect, analyze and interpret the signals. In this paper we revisit GW150914, presenting updated estimates of its source parameters using a waveform model developed within the EOB formalism, able to describe gravitational-wave emission from generic non-circular, non-planar binaries. We provide a comprehensive analysis of the signal and its properties, considering and contrasting various scenarios for the source: from the simplest, aligned-spin quasi-circular binary black hole merger, to more complex scenarios, including precession, eccentricity or both. Unsurprisingly, we find that the signal is consistent with a quasi-circular ($e < 0.08$ at $15$ Hz), slowly spinning $(χ_{\rm eff} = -0.03^{+0.12}_{-0.13})$ binary black hole merger, a-posteriori validating a considerable body of works. This is the first analysis performed with an inspiral-merger-ringdown model containing both eccentricity and precession.

gr-qc↗

arXiv2024

Blind spots and biases: the dangers of ignoring eccentricity in gravitational-wave signals from binary black holes

Most gravitational wave (GW) events observed by the LIGO and Virgo detectors are consistent with mergers of binary black holes (BBHs) on quasi-circular orbits. However, some events are also consistent with non-zero orbital eccentricity, which can indicate that the binary formed via dynamical interactions. Active GW search pipelines using quasi-circular waveform templates are inefficient for detecting eccentric mergers. Also, analysing eccentric GW signals with waveform models neglecting eccentricity can lead to biases in the recovered parameters. We explore the detectability and characterisation of eccentric signals when searches and analyses rely on quasi-circular waveform models. We find that for a reference eccentric population, the fraction of events having fitting factor (FF) $< 0.95$ can be up to $\approx 2.2\%$ compared to $\approx 0.4\%$ for the baseline population. This leads to the loss in signal recovery fraction for up to $6\%$ for parameter space with non-negligible eccentricity ($e_{10} > 0.01$) and high mass ratio ($q > 3$). We perform parameter estimation (PE) for non-spinning and aligned-spin eccentric GW injections from BBHs with a total mass $M=35 M_\odot$, based on numerical relativity simulations and an EOB based inspiral-merger-ringdown model (TEOBResumS). We recover these injections using both quasi-circular and eccentric waveform models. For cases with $e_{20} \sim 0.1$, quasi-circular models fail to estimate chirp mass within the 90% credible interval accurately. Further, for these low-mass injections, spin-induced precession does not mimic eccentricity. For injections of $e_{20}\sim 0.1$, PE conducted with an inspiral-only eccentric waveform model correctly characterises the injected signal to within 90% confidence, and recovers the injected eccentricities, suggesting that such models are sufficient for characterisation of low-mass eccentric BBH. (abridged)

gr-qc↗