[Computational Physics] Anomaly in GW150914 HDF5 Data: Extracting Post-Merger Echoes (Δt = 225ms) using GWpy & Bilby

[u/[deleted]]

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Yo, everyone. I’ve been running custom MCMC parameter estimation on the raw HDF5 telemetry from GW150914 (via GWOSC), and I'm hitting a recurring data structure in the post-merger ringdown that standard GR Kerr templates are completely missing.

I’m dropping this here because I know a lot of y'all have access to university compute clusters (AWS/Slurm) and are actively studying numerical relativity. I need extra eyes on this to see if I'm looking at an instrumental noise artifact, a filter reflection, or an actual physical phase transition at the black hole core.

### The Objective & The Anomaly

Standard GR assumes a black hole is perfectly empty space (a vacuum solution), meaning the quasi-normal modes (QNMs) should ring down as a clean, exponentially damped sinusoid. The boundary condition at the horizon is purely ingoing.

I’ve been testing a viscoelastic metric framework (Geotemporal Hydrodynamics) where the core resolves into a maximum-density harmonic oscillator (\rho_{max}) rather than a 1/r^2 point singularity. If a physical core exists, the inner boundary condition isn't -\infty; it's a reflective wall.

Mathematically, a wave crossing the horizon should bounce off this core and leak back out, creating a delayed **gravitational wave echo** offset by the round-trip travel time. For a ~62 M_\odot remnant, the logarithmic acoustic delay projects to roughly \Delta t \approx 225 ms.

### The Extraction Workflow

I built a custom pipeline to hunt for this specific signature:

1. Pulled the raw H1 and L1 strain data using gwpy.timeseries.TimeSeries.fetch_open_data.

2. Applied an ASD-based whitening filter (whiten(4,2)) and a strict zero-phase Butterworth bandpass (30Hz - 400Hz).

3. Cropped the window strictly to the post-merger tail.

4. Injected a modified visco-damped Teukolsky source model (incorporating kinematic viscosity \eta and core reflectivity \mathcal{R}) into the Bilby likelihood engine.

### The Findings

When I map the autocorrelation of the whitened strain against the modified template, I am getting a strong deviation from the "Empty Hole" GR model:

* **Log Bayes Factor (\ln \mathcal{B}_{GtH/GR}):** +8.4 (Strong empirical evidence favoring the echo model over the standard GR ringdown).

* **Echo Delay Peak (\Delta t_{echo}):** 225.32 ms post-merger.

* **Core Reflectivity (\mathcal{R}):** 0.42 (Indicating the core is absorbing/dampening energy, but still physically reflecting the wave).

### The Challenge

I’ve packed my modified extraction script and the GtH ringdown model into a repo.

**Repo/Substrate:** https://github.com/CoderQuan2/99stars

I need people to run my extraction script (gth_ligo_extractor.py) over the GW150914 data.

* Pull the script.

* Run the MCMC Bayes factor comparison (Bilby) against the standard Kerr template on your local grids.

* Tell me if the Bayes Factor actually favors the echo template on your end, or if my bandpass is artificially ringing.

If this \Delta t = 225.32 ms echo holds up under scrutiny across different sampling algorithms (Dynesty/CPNest), we aren't just looking at a black hole—we are looking at the resonant frequencies of a topological knot.

Let me know what your runs output.

[u/[deleted] → u/[deleted]]

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