Combining post-circular and Padé approximations to compute Fourier domain templates for eccentric inspirals
Srishti Tiwari, A. Gopakumar
Abstract
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 ${e}_{0}\ensuremath{\le}0.2$. We here explore the possibility of combining post-circular and Pad\'e approximations to obtain fully analytic frequency domain eccentric inspiral templates. The resulting 1PN-accurate approximant is capable of faithfully capturing eccentric inspirals having ${e}_{0}\ensuremath{\le}0.6$ while employing our 1PN extension of a frequency domain template family that does not use post-circular approximation, detailed in [B. Moore et al., Classical Quantum Gravity 35, 235006 (2018)]. We also discuss subtleties that arise while combining post-circular and Pad\'e approximations to obtain higher PN order templates for eccentric inspirals.