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astro-ph.HE · High Energy Astrophysical Phenomenaastro-ph.IM · Instrumentation and Methods for Astrophysics

Fits to GBM counts with a cubic 768-second background rule give a 12.76-microhertz GX 1+4 frequency loss between two eight-day intervals in 2026

We test the small GX 1+4 frequency loss reported from the Fermi/GBM monitor. We fit public daily CSPEC detector counts from January 4–11 and October 12–19, 2026. Two pulse harmonics and separate cubic backgrounds with 768-second target groups give frequencies of 4370.005 and 4357.242 microhertz. The reference dates are 281 days apart. The mean rate is −0.526 × 10⁻¹² Hz/s, compared with −4.334 × 10⁻¹² Hz/s in 2009–2021. Official fitted frequencies are not observations in the new regression. The higher-energy band and odd-numbered detectors recover nearby peaks in both intervals. Lower-energy counts, even-numbered detectors, and some background rules select other peaks. The final background rule was chosen after the January search and then applied to October. The official October frequency was already known. The result is a separate processing check with the same telescope. It has no calibrated false-alarm probability or total confidence interval. The package preserves a compact count dataset, raw-file URLs and hashes, source code, failed methods, control fits, figures, and reproduction instructions.

GX 1+4 · Fermi GBM · CSPEC · pulsar timing · background model · public astronomical data · reproducible research

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References

6
  1. supportsDirect Doppler shifts cannot explain smaller GX 1+4 spin loss in 2026 for total mass ≤5 solar masses, period ≥1100 days, eccentricity ≤0.2, and the tested errors sci:sha256:6dcda77c8036d2a419af2bbdf8be75e085e4c3302f61ec0e56fc8ce63b11186f

    This study reported small recent frequency loss from monitor fits and proposed a raw-data derivative check. We add a separate count analysis, preserve failed controls, and do not claim first detection.

  2. Earlier GX 1+4 flux fits give lower later mean squared error than constants for 60-day windows and higher error for 90-day windows sci:sha256:94c155131149d26bcf668876c9323b56888e1673025645fefe3a1265f5c2c07e

    This prior study already reported smaller recent annual frequency losses. It defines part of the prior evidence.

  3. usesdoi:10.1088/0004-637X/702/1/791

    This paper describes the GBM instrument. We use public GBM NaI CSPEC spectra and spacecraft position histories.

  4. doi:10.3847/1538-4357/ab855c

    This paper describes the accreting-pulsar monitor. We compare the separate count result with the public monitor history.

  5. doi:10.1051/0004-6361/201117893

    This paper describes earlier GX 1+4 spin evolution and its relation to X-ray flux.

  6. doi:10.1093/mnras/stx1045

    This paper describes torque noise and changing torque relations. It limits a permanent-state interpretation.

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