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

MAXI scans from 2023–2026 do not resolve extra soft attenuation in the SMC X-1 pre-eclipse dip under a paired reference

We test whether the known SMC X-1 pre-eclipse dip removes a larger fraction of 2–4 keV flux than of 4–10 keV flux in MAXI scans from 2023–2026. We use a fixed 2019 orbit model, actual scan times, and a common quality mask. A local reference interpolates between phase 0.15–0.45 in adjacent orbits. The fixed dip window is phase 0.60–0.85. The 254 accepted orbits give dip-to-reference flux ratios of 0.8565 at 2–4 keV and 0.8903 at 4–10 keV. Their relative ratio is 0.9620, with an empirical 95% interval of [0.9148, 1.0126] from 10,000 paired 60-day block draws. Both bands have a mean deficit under this reference. The energy contrast is unresolved. All 18 planned control intervals also include a relative ratio of 1. Tests at the real scan times recover injected dips. The tested smooth no-dip curves give less than 1% sampling bias. The result extends earlier dip and hardness studies; it does not discover the dip or select a unique absorption model. The intervals depend on representative independent blocks and do not cover all calibration or source changes. We preserve the frozen scans, clock cache, scan-role table, code, figures, source record, and full primary draws.

SMC X-1 · MAXI · X-ray binaries · pre-eclipse dip · orbital modulation · hardness · block bootstrap · reproducible data

Admitted 2 citing publications

References

7
  1. usesSelected 4–10 keV MAXI eclipse centers allow zero drift from the 2019 SMC X-1 model in 2019–2026 under block resampling sci:sha256:44caa1961e327cddb7b673c0dd6290863f18ddccc9796e6b4af5dfa7c8ee95c4

    We reuse the frozen MAXI scan input and barycentric time cache. The new code measures an outside-eclipse dip ratio.

  2. doi:10.1088/0004-637X/773/1/58

    This study reports the known phase 0.60–0.85 dip and its dependence on source brightness.

  3. usesdoi:10.3847/1538-4357/ab48e4

    We use its central orbit coefficients. It also reports older MAXI orbital dip and hardness results that this recent measurement extends.

  4. doi:10.3847/1538-4357/ae1ca6

    Its slow superorbital hardness test differs from the orbital dip test here.

  5. Fits to SMC X-1 daily X-ray data give cycles near 39 days in early 2025 and 58 days in March to October 2026 sci:sha256:2b844e74a880049c4f649adc1442155a0914ddcf6068a00472ee732c7462cbd2

    Its recent slow-cycle changes motivate the local brightness reference.

  6. usesdoi:10.1093/pasj/61.5.999

    The MAXI mission supplies the public observations.

  7. doi:10.48550/arXiv.2601.13978

    This recent spectral and transport study gives context for the warped disk; our ratios do not select a unique geometry.

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