TY - JOUR

T1 - Inferring spin tilts of binary black holes at formation with plus-era gravitational wave detectors

AU - Kulkarni, Sumeet

AU - Johnson-Mcdaniel, Nathan K.

AU - Phukon, Khun Sang

AU - Krishnendu, N. V.

AU - Gupta, Anuradha

N1 - Funding Information: We thank Serguei Ossokine for carefully reading the manuscript and providing helpful comments and the anonymous referee for useful suggestions. N. K. J-M. is supported by the NSF Grant No. AST-2205920. A. G. is supported in part by NSF Grants No. AST-2205920 and No. PHY-2308887. K. S. P. acknowledges support from the Dutch Research Council (NWO). N. V. K. is thankful to the Max Planck Society’s Independent Research Group Grant and the Science and Engineering Research Board National Post Doctoral Fellowship (N-PDF). The authors are grateful for computational resources provided by the LIGO Lab and supported by NSF Grants No. PHY-0757058 and No. PHY-0823459. We also acknowledge the use of the Maple cluster at the University of Mississippi (funded by NSF Grant No. CHE-1338056), the IUCAA LDG cluster Sarathi, the University of Birmingham’s BlueBEAR HPC service, Nikhef’s Visar cluster, and Max Planck Computing and Data Facility’s clusters Raven and Cobra for the computational/numerical work. This research has made use of p arallel b ilby v1.1.3 , a parallelized Bayesian inference p ython package, and dynesty v1.1 , a nested sampler, to perform Bayesian parameter estimation. The software packages a stropy , lals uite , m atplotlib , n um p y , p andas , pes ummary , s ci p y , and s eaborn were utilized for data analysis. This is LIGO document P2300128.

PY - 2024/2/2

Y1 - 2024/2/2

N2 - The spin orientations of spinning binary black hole (BBH) mergers detected by ground-based gravitational wave detectors such as LIGO and Virgo can provide important clues about the formation of such binaries. However, these spin tilts, i.e., the angles between the spin vector of each black hole and the binary's orbital angular momentum vector, can change due to precessional effects as the black holes evolve from a large separation to their merger. The tilts inferred at a frequency in the sensitive band of the detectors by comparing the signal with theoretical waveforms can thus be significantly different from the tilts when the binary originally formed. These tilts at the binary's formation are well approximated in many scenarios by evolving the BBH backward in time to a formally infinite separation. Using the tilts at infinite separation also places all binaries on an equal footing in analyzing their population properties. In this paper, we perform parameter estimation for simulated BBHs and investigate the differences between the tilts one infers directly close to merger and those obtained by evolving back to infinite separation. We select simulated observations such that their configurations show particularly large differences in their orientations close to merger and at infinity. While these differences may be buried in the statistical noise for current detections, we show that in future plus-era (A+ and Virgo+) detectors, they can be easily distinguished in some cases. We also consider the tilts at infinity for BBHs in various spin morphologies and at the endpoint of the up-down instability. In particular, we find that we are able to easily identify the up-down instability cases as such from the tilts at infinity.

AB - The spin orientations of spinning binary black hole (BBH) mergers detected by ground-based gravitational wave detectors such as LIGO and Virgo can provide important clues about the formation of such binaries. However, these spin tilts, i.e., the angles between the spin vector of each black hole and the binary's orbital angular momentum vector, can change due to precessional effects as the black holes evolve from a large separation to their merger. The tilts inferred at a frequency in the sensitive band of the detectors by comparing the signal with theoretical waveforms can thus be significantly different from the tilts when the binary originally formed. These tilts at the binary's formation are well approximated in many scenarios by evolving the BBH backward in time to a formally infinite separation. Using the tilts at infinite separation also places all binaries on an equal footing in analyzing their population properties. In this paper, we perform parameter estimation for simulated BBHs and investigate the differences between the tilts one infers directly close to merger and those obtained by evolving back to infinite separation. We select simulated observations such that their configurations show particularly large differences in their orientations close to merger and at infinity. While these differences may be buried in the statistical noise for current detections, we show that in future plus-era (A+ and Virgo+) detectors, they can be easily distinguished in some cases. We also consider the tilts at infinity for BBHs in various spin morphologies and at the endpoint of the up-down instability. In particular, we find that we are able to easily identify the up-down instability cases as such from the tilts at infinity.

UR - http://www.scopus.com/inward/record.url?scp=85184020868&partnerID=8YFLogxK

U2 - 10.48550/arXiv.2308.05098

DO - 10.48550/arXiv.2308.05098

M3 - Article

AN - SCOPUS:85184020868

VL - 109

JO - Physical Review D

JF - Physical Review D

SN - 2470-0010

IS - 4

M1 - 043002

ER -