arXiv subjects

James Paynter

Publications and source records attributed to James Paynter.

2 recordsLinked to original sources

arXiv2023

Meet the parents: the progenitor binary for the supermassive black hole candidate in E1821+643

The remnants of binary black hole mergers can be given recoil kick velocities up to $5,000\text{ km s$^{-1}$}$ due to anisotropic emission of gravitational waves. E1821+643 is a recoiling supermassive black hole moving at $\sim 2,100\text{ km s$^{-1}$}$ along the line-of-sight relative to its host galaxy. This suggests a recoil kick of $\sim 2,240\text{ km s$^{-1}$}$. Such a kick is powerful enough to eject E1821+643 from its $M_\text{gal}\sim 2 \times 10^{12}\text{ M}_{\odot}$ host galaxy. In this work, we address the question: what are the likely properties of the progenitor binary that formed E1821+643? Using astrophysically motivated priors, we infer that E1821+643 was likely formed from a binary black hole system with masses of $m_1\sim 1.9^{+5.0}_{-3.8}\times 10^{9}\text{ M}_{\odot}$, $m_2\sim 8.1^{+3.9}_{-3.2} \times 10^{8}\text{ M}_{\odot}$ (90\% credible intervals). The black holes in this binary were likely to be spinning rapidly with dimensionless spin magnitudes of $χ_1 = 0.87^{+0.11}_{-0.26}$, $χ_2 = 0.77^{+0.19}_{-0.37}$. Such a high recoil velocity is impossible for spins aligned to the orbital angular momentum axis. This suggest that E1821+643 merged in hot gas, which is thought to provide an environment where spin alignment from accretion proceeds slowly relative to the merger timescale. We infer that E1821+643 is likely to be rapidly rotating with dimensionless spin $χ = 0.92\pm0.04$. A $2.6 \times 10^9 \text{ M}_{\odot}$ black hole, recoiling from a gas-rich environment at $v\sim 2,240\text{ km s$^{-1}$}$ is likely to persist as an active galactic nuclei for $\sim 860$ Myr, in which time it traverses $\sim 2$ Mpc.

astro-ph.GA↗

arXiv2021

Evidence for an intermediate-mass black hole from a gravitationally lensed gamma-ray burst

If gamma-ray bursts are at cosmological distances, they must be gravitationally lensed occasionally. The detection of lensed images with millisecond-to-second time delays provides evidence for intermediate-mass black holes, a population that has been difficult to observe. Several studies have searched for these delays in gamma-ray burst light curves, which would indicate an intervening gravitational lens. Among the $\sim 10^4$ gamma-ray bursts observed, there have been a handful of claimed lensing detections, but none have been statistically robust. Here we present a Bayesian analysis identifying gravitational lensing in the light curve of GRB950830. The inferred lens mass depends on the unknown lens redshift $z_l$, and is given by $(1+z_l)M_l = 5.5^{+1.7}_{-0.9}\times 10^4 $ M$_\odot$ (90% credibility), which we interpret as evidence for an intermediate-mass black hole. The most probable configuration, with a lens redshift $z_l\sim 1$ and a gamma-ray burst redshift $z_s\sim 2$, yields a present day number density of $n_\text{imbh}\approx 2.3^{+4.9}_{-1.6}\times10^{3} \text{ Mpc}^{-3}$ (90% credibility) with a dimensionless energy density $Ω_\text{imbh} \approx 4.6^{+9.8}_{-3.3}\times10^{-4}$. The false alarm probability for this detection is $\sim0.6\%$ with trial factors. While it is possible that GRB950830 was lensed by a globular cluster, it is unlikely since we infer a cosmic density inconsistent with predictions for globular clusters $Ω_\text{gc} \approx 8 \times 10^{-6}$ at 99.8% credibility. If a significant intermediate-mass black hole population exists, it could provide the seeds for the growth of supermassive black holes in the early Universe.

astro-ph.HE↗