arXiv subjects

Srishti Tiwari

Publications and source records attributed to Srishti Tiwari.

4 recordsLinked to original sources

arXiv2025

Constraining initial orbital eccentricity of inspiral-dominated gravitational-wave events with an analytic approximant

The LIGO-Virgo-KAGRA consortium has sporadically detected inspiral-dominated gravitational-wave events such as GW170817 and GW190425. These events offer an opportunity to constrain possible initial (residual) orbital eccentricities using inspiral template families. We detail an LALSuite approximant, TaylorF2Ecck, which analytically models inspiral gravitational waves from nonspinning compact binaries in post-Newtonian (PN)-accurate eccentric orbits and restricts initial-eccentricity contributions to leading order. Specifically, our frequency-domain approximant consistently incorporates orbital, advance of periastron, and gravitational-wave emission effects up to 3PN order. We conduct parameter-estimation studies of GW170817 and GW190425 using TaylorF2Ecck, following comprehensive sanity checks to validate model performance and investigate the influence of eccentricity and periastron advance in the relevant parameter space. The results indicate that the initial eccentricity at 20 Hz is negligible within the 90 percent credible intervals (less than 0.016 for GW170817 and less than 0.023 for GW190425, with both posterior distributions railing toward zero), and Bayes factors show no strong evidence favoring the eccentric waveform over the quasicircular waveform. At such negligible initial eccentricities, comparisons between eccentric models with and without periastron advance show no clear signature of this effect, with no significant model-dependent shifts in the posterior distributions and no strong Bayes-factor evidence favoring one model over the other. Additionally, these detailed studies reveal the importance of incorporating initial-eccentricity contributions at least up to 3.5PN order and discuss its implications. We substantiate this inference using versions of the quasicircular TaylorF2 approximant that incorporate Fourier phase contributions beyond the conventional 3.5PN order.

astro-ph.HE↗

arXiv2022

Towards establishing the presence or absence of horizons in coalescing binaries of compact objects by using their gravitational wave signals

The quest for distinguishing black holes (BH) from horizonless compact objects using gravitational wave (GW) signals from coalescing compact binaries can be helped by utilizing the phenomenon of tidal heating (TH), which leaves its imprint on binary waveforms through the horizon parameters. We investigate the effects of TH on GWs to probe the observability of the horizon parameters, mainly using Fisher matrix analysis to determine the errors and covariances between them. The horizon parameters are defined as $H_1$ and $H_2$ for the two binary components, with $H_{1,2} \in [0,1]$, and combined with the component masses and spins to form two new parameters, $H_{\rm eff5}$ and $H_{\rm eff8}$, to minimize their covariances in parameter estimation studies. In this work, we add the phase contribution due to TH in terms of $H_{\rm eff5}$ and $H_{\rm eff8}$ to a post-Newtonian waveform and examine the variation of their measurement errors with the binary's total mass, mass ratio, luminosity distance, and component spins. Since the Fisher matrix approach works well for high signal-to-noise ratio, we focus mainly on third-generation (3G) GW detectors Einstein Telescope and Cosmic Explorer and use LIGO and Virgo for comparison. We find that the region in the total binary mass where measurements of $H_{\rm eff5}$ and $H_{\rm eff8}$ are most precise are $\sim 20 - 30M_\odot$ for LIGO-Virgo and $\sim 50 - 80M_\odot$ for 3G detectors. Higher component spins allow more precise measurements of $H_{\rm eff5}$ and $H_{\rm eff8}$. For a binary situated at 200 Mpc with component masses $12M_\odot$ and $18M_\odot$, equal spins $χ_1=χ_2=0.8$, and $H_{\rm eff5}=0.6$, $H_{\rm eff8}=12$, the 1-$σ$ errors in these two parameters are $\sim 0.01$ and $\sim 0.04$, respectively, in 3G detectors. We substantiate our results from Fisher studies with a set of Bayesian simulations.

gr-qc↗

arXiv2020

Combining Post-Circular and Padé approximations to compute Fourier domain templates for eccentric inspirals

Observations of transient gravitational wave (GW) events with non-negligible orbital eccentricity can be highly rewarding from astrophysical considerations. Ready-to-use fully analytic frequency domain inspiral GW templates are crucial ingredients to construct eccentric inspiral-merger-ringdown waveform families, required for the detection of such GW events. It turns out that a fully analytic, post-Newtonian (PN) accurate frequency domain inspiral template family, which uses certain post-circular approximation, may only be suitable to model events with initial eccentricities $e_0 \leq 0.2$.We here explore the possibility of combining Post-Circular and Padé approximations to obtain fully analytic frequency domain eccentric inspiral templates. The resulting 1PN-accurate approximant is capable of faithfully capturing eccentric inspirals having $e_0 \leq 0.6$ while employing our 1PN extension of a frequency domain template family that does not use post-circular approximation, detailed in Moore, B., et al.\ 2018, Classical and Quantum Gravity, 35, 235006. We also discuss subtleties that arise while combining post-circular and Padé approximations to obtain higher PN order templates for eccentric inspirals.

gr-qc↗

arXiv2019

Ready-to-use Fourier domain templates for compact binaries inspiraling along moderately eccentric orbits

We derive analytic expressions that provide Fourier domain gravitational wave (GW) response function for compact binaries inspiraling along moderately eccentric orbits. These expressions include amplitude corrections to the two GW polarization states that are accurate to the first post-Newtonian (PN) order. Additionally, our fully 3PN accurate GW phase evolution incorporates eccentricity effects up to sixth order at each PN order. Further, we develop a prescription to incorporate analytically the effects of 3PN accurate periastron advance in the GW phase evolution. This is how we provide a ready-to-use and efficient inspiral template family for compact binaries in moderately eccentric orbits. Preliminary GW data analysis explorations suggest that our template family should be required to construct analytic inspiral-merger-ringdown templates to model moderately eccentric compact binary coalescence.

gr-qc↗