Pulsar timing array signals induced by black hole binaries in relativistic eccentric orbits

Abstract

Individual supermassive black hole binaries in non-circular orbits are possible nanohertz gravitational wave sources for the rapidly maturing Pulsar Timing Array experiments. We develop an accurate and efficient approach to compute Pulsar Timing Array signals due to gravitational waves from inspiraling supermassive black hole binaries in relativistic eccentric orbits. Our approach employs a Keplerian-type parametric solution to model third post-Newtonian accurate precessing eccentric orbits while a novel semi-analytic prescription is provided to model the effects of quadrupolar order gravitational wave emission. These inputs lead to a semi-analytic prescription to model such signals, induced by non-spinning black hole binaries inspiralling along arbitrary eccentricity orbits. Additionally, we provide a fully analytic prescription to model Pulsar Timing Array signals from black hole binaries inspiraling along moderately eccentric orbits, influenced by Boetzel et al. [Phys. Rev. D 96,044011(2017)]. These approaches are being incorporated into Enterprise and TEMPO2 for searching the presence of such binaries in Pulsar Timing Array datasets.

Spitzer Observations of the Predicted Eddington Flare from Blazar OJ 287

“…We presented observational evidence and astrophysical arguments for the occurrence of an impact flare during 2019 July 31 in OJ287 that was predicted using the BBH central engine model. These efforts confirm OJ287 as a source of nano-Hz GWs, which should provide additional motivation for probing the IPTA data sets for GWs from massive BH binaries in general relativistic eccentric orbits (Susobhanan et al 2020). The present analysis underlines the importance of incorporating the effects of higher-order GW emission in the model.…”

Promise of Persistent Multi-Messenger Astronomy with the Blazar OJ 287

“…Therefore, it is important to develop prescriptions to model the expected pulsar timing array (PTA) response to nHz inspiral GWs from systems like OJ 287 [10]. The fact that the orbital eccentricity and primary BH spin can substantially influence the BH binary orbital evolution, as demonstrated in [33,114], prompted us to employ an improved version of GW phasing approach to model temporally evolving GW polarization states from such systems [115][116][117]. This is required as the PTA relevant GW-induced pre-fit pulsar timing residual, namely PTA response to inspiral GWs, induced by an isolated GW source at a given epoch t may be written as [118]…”

“…where τ P is the geometric time delay in the solar system barycenter (SSB) frame of the underlying millisecond pulsar while t and t are the SSB relevant coordinate time variables. Further, h(t) provides the effective GW strain induced by an isolated source at an epoch t and depends on the intrinsic parameters of the GW source like the total mass, spin values, orbital eccentricity and angles that specify its sky location, as detailed in [116]. In other words, PTA response of a pulsar to inspiral GWs from OJ 287 like system at a time t depends not only on the strength of the inspiral GWs at the SSB at t but also on the GW amplitude at location of the pulsar at time t − τ P .…”

“…In other words, PTA response of a pulsar to inspiral GWs from OJ 287 like system at a time t depends not only on the strength of the inspiral GWs at the SSB at t but also on the GW amplitude at location of the pulsar at time t − τ P . This is another reason why we need to employ PN approximation to track the orbital evolution and the resulting GW polarization states while modeling PTA response to inspiral GWs from SMBH binaries [116].…”

pinta: The uGMRT data processing pipeline for the Indian Pulsar Timing Array

“…Ubiquitous galaxy mergers are expected to force their resident supermassive black holes to merge (Berczik et al 2006; Pearson et al 2019). During such merger and the preceding inspiral phases, the black hole pairs are expected to emit gravitational waves (GWs) in the nanohertz frequency range (Burke-Spolaor et al 2019; Susobhanan et al 2020). Pulsar Timing Arrays (PTAs: Hobbs & Dai 2017) aim to detect such GWs by accurately timing the arrival of pulses from an ensemble of millisecond pulsars (MSPs) as these are very precise celestial clocks (Hobbs et al 2020).…”