FEADME: Fast Elliptical Accretion Disk Modeling Engine

Nicholas Earl, K. Decker French, Jason T. Hinkle, Yashasvi Moon, Margaret Shepherd, Margaret E. Verrico

First listed 2025-12-11 | Last updated 2025-12-11

Abstract

We present FEADME (Fast Elliptical Accretion Disk Modeling Engine), a GPU-accelerated Python framework for modeling broad Balmer-line emission using a relativistic elliptical accretion-disk formalism. Leveraging Jax and NumPyro for differentiable forward modeling and efficient Bayesian inference, FEADME enables large-sample, reproducible analyses of disk-dominated emission-line profiles. We apply the framework to 237 double-peaked emitters (DPEs) from the literature and to five tidal disruption events (TDEs) with disk-like H$α$ emission, fitting three physically motivated model families per spectrum and selecting the preferred model using approximate leave-one-out (LOO) cross-validation. We find that AGN exhibit a broad, continuous distribution of disk geometries and kinematics, with significant diversity in disk parameters. Most TDE disk parameter distributions are statistically indistinguishable from those of the AGN, with the sole robust difference being that TDE disks are significantly more circular, consistent with rapid debris circularization in tidal disruption events. The majority of both AGN and TDEs favor models that include both a disk and an additional broad-line component, suggesting that disk emission commonly coexists with more isotropic or wind-driven gas. These results indicate that once a line-emitting disk forms, its spectroscopic appearance is governed by similar physical processes in both persistent AGN and transient TDE accretion flows, and they demonstrate the utility of FEADME for population-level studies of disk structure in galactic nuclei.

Short digest

Introduces FEADME, a GPU-accelerated JAX/NumPyro engine for Bayesian modeling of broad Balmer profiles with a relativistic elliptical accretion-disk formalism. Applied to 237 double-peaked emitters and five TDEs, it fits three model families per spectrum and selects via approximate LOO cross-validation. AGN span a broad, continuous range of disk geometries/kinematics, while TDE disks are the clear outlier only in being more circular; most objects favor a disk plus an added broad-line component. This points to shared line-formation physics once a disk forms and establishes a scalable path to population-level constraints on disk structure in galactic nuclei.

Key figures to inspect

• Figure 1: Inspect the single-epoch Hα profiles for AT 2018hyz, AT 2018zr, AT 2020nov, AT 2020zso, and PTF09djl to gauge peak separations, asymmetries, and how the epoch’s offset from optical peak situates each TDE along its circularization timeline.
• Figure 2: Compare the disk+BLR, no-BLR, and no-disk fits; check wing residuals and the Hα core to see where the added broad Gaussian is required versus where the elliptical disk alone suffices.
• Figure 3: Read the aggregated posteriors for inclination, emissivity index, turbulence, inner/outer radii, apocenter angle, and eccentricity; verify the TDE shift to lower eccentricity (and smaller Rout) relative to AGN clusters, using the median bars for quantitative contrast.
• Figure 4: Use the UMAP+HDBScan map to identify dominant AGN morphological clusters and the grey transitional population; assess whether disk-parameter manifolds show clear boundaries or continuous bridges between groups.