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astro-ph.SR · Solar and Stellar Astrophysicsastro-ph.IM · Instrumentation and Methods for Astrophysics

Joint pulse fits give a higher beat to spin amplitude ratio for FO Aquarii in its 2025 TESS visit than in 2021

FO Aquarii is a binary system with a magnetic white dwarf. We test whether its beat to spin pulse amplitude ratio changed between the public 120-second TESS visits in 2021 and 2025. A joint fit separates the spin pulse, orbit harmonics, nearby pulse frequencies, and slow flux changes. The coherent beat to spin semi-amplitude ratio rises from 0.3436 to 0.4541. The relative increase is 32.2%, with a conditional 95% interval from 19.8% to 45.6%. This interval assumes the fitted pulse model, independent visits, and one-day noise blocks. Changes to the flux product, model terms, and block length support the direction of the change. Both visit halves also support that direction. The result applies to these two visits and this coherent pulse estimator. It does not identify a unique physical cause. Earlier work studied the 2021 pulses and used both visits for eclipse times. This contribution measures the change between visits. The package supplies original archive files, data hashes, source code, fit results, three figures, and instructions to repeat the work.

FO Aquarii · TESS · intermediate polars · magnetic white dwarfs · pulse amplitudes · public data · reproducible research

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References

7
  1. usesdoi:10.3847/2515-5172/ac9bf7

    The reported K2 and 2021 TESS pulse patterns motivate a test of the two later TESS visits.

  2. doi:10.3847/1538-4365/ad43ec

    This survey compares orbit waveforms for FO Aquarii with K2 and TESS sector 42 data.

  3. supportsdoi:10.3847/1538-4365/addf41

    The reported 2021 beat to spin peak power ratio agrees closely with the square of our 2021 amplitude ratio. The methods differ. This survey does not include the 2025 visit.

  4. usesdoi:10.48550/arXiv.2509.22786

    This eclipse study identifies and uses the same 2021 and 2025 TESS visits. It provides context for the data and the orbit. We measure a different property of those data.

  5. usesdoi:10.1093/mnras/stw834

    The fit uses the established spin, orbit, and related pulse frequencies studied in K2 data.

  6. usesdoi:10.1016/S1384-1076(96)00008-5

    The fixed orbit period of 0.20205976 days locates pulse frequencies within each visit.

  7. usesdoi:10.17909/g203-sd46

    The two original 120-second SPOC light curves come from this public TESS data collection. Exact product addresses and hashes are preserved.

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