arXiv subjects

Madeline Clyburn

Publications and source records attributed to Madeline Clyburn.

3 recordsLinked to original sources

arXiv2026

Unequal Mass Binary Evolution Driven by High Mach Circumbinary Disks

We present a study of the gas-driven orbital evolution of unequal mass black hole binaries with circumbinary gas disks (CBDs), varying Mach number and viscosity (nu). Using two-dimensional grid-based hydrodynamics simulations spanning a thousand binary orbits at fixed separation, we explore low to moderate mass ratios (q = 0.05-1.0) and examine how variations in Mach and q affect the torques and component accretion rates exerted by the CBD and consequently the binary evolution. Equal mass binary systems receive positive torques in low-mach disks but transition to negative torques for Mach >25. As q decreases, the transition moves to higher Mach numbers. For q<0.1, we find no torque sign reversal below Mach~52, except in sufficiently low-viscosity disks. We find that the secondary black hole cannot effectively repel the CBD, it instead accretes most of the inflowing gas from the CBD; these low mass ratio binaries in high viscosity disks therefore tend to outspiral, although inspiral can occur in less viscous environments. We also find that binaries with mass ratios in the range of 0.25 - 0.5 can show preferential accretion favoring the primary when the gas viscosity is low, exemplifying an exception to the established rule of thumb that accretion favors the secondary. We discuss differences between our results and those reported in the literature on the orbital evolution and preferential accretion, and emphasize that our simulations extend into a regime that remains largely unexplored. Overall, our results suggest that intermediate mass ratio inspirals (IMRIs) in CBDs may be less frequent, but this depends sensitively on the interplay between mass ratio, disk temperature, and viscosity.

astro-ph.HE↗

arXiv2025

The dynamics and electromagnetic signatures of accretion in unequal mass binary black hole inspirals

We present a theoretical study of the gravitational wave (GW) driven inspirals of accreting black hole binaries with mass $M = 10^7 M_\odot$ and mass ratios between $10^{-3}$ and $10^{-1}$. Our results are based on analytic estimates, and grid-based hydrodynamics simulations run for many thousands of binary orbits before the merger. We show that the GW inspiral is evident in the light curves and color evolution of a binary-hosting quasar, over years to decades before a merger. The long-term electromagnetic (EM) signature is characterized by a gradual UV brightening, and X-ray dimming, followed by an X-ray disappearance hours to days before the GW burst, and finally a years-like re-brightening as the disk relaxes and refuels the remnant black hole. These timescales are surprisingly insensitive to the amplitude of viscous stress in the disk. The spectrum of quasi-thermal disk emission shows two peaks: one in the UV, and another in the X-ray, associated with the outer and circum-secondary disks respectively; emission from the inner disk is suppressed because the secondary consumes most of the inflowing gas. We discuss implications for real-time and archival EM followup of GW bursts detected by LISA.

astro-ph.HE↗

arXiv2024

Changing-Look Inspirals: Trends and Switches in AGN Disk Emission as Signposts for Merging Black Hole Binaries

Using grid-based hydrodynamics simulations and analytic modeling, we compute the electromagnetic (EM) signatures of gravitational wave (GW) driven inspirals of massive black hole binaries that accrete gas from circumbinary disks, exploring the effects of varying gas temperatures, viscosity laws, and binary mass ratios. Our main finding is that active galactic nuclei (AGN's) that host inspiraling binaries can exhibit two sub-types of long-term secular variability patterns: Type-A events which dim before merger and brighten afterward, and Type-B events which brighten before merger and dim afterward. In both types the merger coincides with a long-lasting chromatic change of the AGN appearance. The sub-types correspond to the direction of angular momentum transfer between the binary and the disk, and could thus have correlated GW signatures if the gas-induced torque can be inferred from GW phase drift measurements by LISA. The long-term brightness trends are caused by steady weakening of the disk-binary torque that accompanies orbital decay, it induces a hysteresis effect whereby the disk "remembers" the history of the binary's contraction. We illustrate the effect using a reduced model problem of an axisymmetric thin disk subjected at its inner edge to the weakening torque of an inspiraling binary. The model problem yields a new class of self-similar disk solutions, which capture salient features of the multi-dimensional hydrodynamics simulations. We use these solutions to derive variable AGN disk emission signatures within years to decades of massive black hole binary mergers in AGN's. Spectral changes of Mrk 1018 might have been triggered by an inspiral-merger event.

astro-ph.HE↗