Henry
Zimmerman

I analyzed six years of OGLE photometry for OGLE-LMC-CEP-1347, a double-overtone binary in the Large Magellanic Cloud with the shortest known orbital period for a Cepheid (58.85 ± 0.08 days). Using a custom prewhitening and Light-Time Travel Effect correction pipeline, I isolated a frequency triplet consistent with a non-radial mode, with spacing $\Delta$f ≈ 0.0074 c/d. I validated this with dual-domain frequency and time-evolution $O-C$ Monte Carlo simulations, finding Prot ≈ 135 ± 15 days. This is over five σ longer than the 58.85 day orbit. Since tidal theory predicts synchronization precedes circularization by $>10$x, this asynchronous rotation in a circular orbit would suggest recent merger spindown.

Update (March 2026): My window function analysis revealed a Δf degeneracy with the 1-year OGLE sampling aliases. After determining the sampling limits of the ground-based photometry, I decided on a methodological pivot. As Co-Investigator and primary author of the Science Justification, I am drafting a VLT/ESPRESSO Phase 1 proposal with Dr. Bogumił Pilecki as PI to obtain phase-constrained chemical abundances. Spectroscopy bypasses these aliases to provide a versatile test of the merger scenario and enable exploration of currently unconstrained stellar evolution scenarios.

For readers interested in the full analysis pipeline, including the alias diagnostic that invalidated the candidate rotational signal, see the Methodological Appendix.

Using photometric measurements from the ALCDEF Light Curve Database, I developed statistical models to estimate period convergence requirements and used those results to design an observing strategy.

To improve observational efficiency under variable viewing conditions, I built an open-source scheduling tool that integrates orbital ephemerides, lunar sky brightness models, and site visibility constraints to prioritize high-quality observing windows. The goal is to reduce wasted telescope time and improve cadence reliability through more reliable phase sampling. The tool recently completed its commissioning with success, coordinating photometry across four observatories in the Canary Islands, Chile, Australia, and Andover to recover a rotational period that's resonant with an Earth day.

The call went out publicly on March 2, featured by Slooh's community team after I coordinated with their staff. Jo booked three Canary One missions that day. Shad0 imaged from Chile Two and Australia One, returned plate-solved files with confirmed ephemeris matches, and asked what else needed filling. Lee scheduled 99 over the following three weeks, lost power to high winds once, taught himself Google Drive to transfer the files, and delivered 80 FITS before Cindygraber faded below the noise floor. Our team is preparing the results for submission to the Minor Planet Bulletin.

A note on methods: I evaluated supervised learning approaches for period convergence prediction early in this project, but found statistical modeling better supported by the dataset characteristics. This work inspired me to separately apply CMA-ES evolutionary optimization to cadence scheduling.

My first independent research target. I remotely operated the Slooh Chile 432mm telescope for two months, performing multi-band (V−I) differential photometry of the classical Cepheid U Sgr in open cluster M25. Sinusoidal light curve fits confirmed the 6.74-day period (R² = 0.93 V-band, 0.70 I-band). V-band distance calculations yielded 40.8% error versus 1.9% in I-band, a direct demonstration of how interstellar dust preferentially scatters shorter wavelengths and why accurate extinction corrections are critical for Cepheid distance work. Strong color index correlation (r = 0.85) provided independent evidence for pulsation, consistent with the kappa-mechanism. The project expanded into an investigation of metallicity-dependent corrections to the period-luminosity relation.