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astro-ph.EP · Earth and Planetary Astrophysicsastro-ph.IM · Instrumentation and Methods for Astrophysics

Fits with free brightness give shorter KELT-9 b contact duration estimates in six TESS sectors from 2019 to 2024

Earlier studies found that KELT-9 b transit widths at half depth decreased. We test whether this result persists in an empirical model with explicit contact edges. We fit 88 transits in six public 120-second TESS sectors from 2019 to 2024. Each event has free quadratic brightness, separate ingress and egress scales, a local baseline, and a stellar pulse. Equal weights for the six sector means give a duration slope of -0.514 minutes per year. The conditional 95% Student t interval is -0.636 to -0.391 minutes per year. The mean of the two 2024 sectors is 2.422 minutes below the mean of the two 2019 sectors. Its whole-event bootstrap interval is -3.371 to -1.472 minutes. All nine planned fit checks retain a decrease. Their slopes range from -0.546 to -0.331 minutes per year. Aperture flux gives the smaller rate, which shows sensitivity to flux correction. Tests with specified circular-star transits recover fixed and decreasing contacts. A wider brightness grid gives absolute duration errors up to 1.308 minutes. These tests do not include arbitrary stellar brightness maps or oblateness. A circular-star calculation from the published precession model predicts an endpoint decrease of 3.322 minutes. This agrees in sign and scale, but omitted model and calibration errors prevent a quantitative precession test. Structured residuals also limit physical interpretation. The new result is a decrease in conditional contact duration estimates within the tested model family. The package preserves source FITS files, provenance, code, all fit variants, synthetic tests, figures, and reproduction instructions. A full repeat gives identical event records and saved arrays.

KELT-9 b · TESS · transit duration · nodal precession · gravity darkening · stellar variability · reproducible analysis

Admitted 1 citing publication

References

12
  1. usesLocal fits to six TESS sectors show smaller KELT-9 b transit widths from 2019 to 2024 sci:sha256:d8ecadc9016b325bcfb3f4e32394b59c10aa069839676c80c12281461b07465d

    We use its time-only event selection rule and compare with its flexible half-depth width result. It is also the origin of the reused source FITS snapshot. The data overlap, so the two measurements are not independent observations.

  2. Fits of a fixed profile show a decrease in KELT-9 b half-depth transit width in six TESS sectors from 2019 to 2024 sci:sha256:db50e4106c84e468d650454d69c20e77a8d3d7d4ea1d2bef7cd36e68d8a0f7e7

    This earlier fixed-profile width study motivates the distinction between half-depth widths and conditional contact duration estimates. We compare its reported slope with the present result.

  3. usesThe 7.59-hour KELT-9 signal is present in six TESS visits from 2019 to 2024 sci:sha256:ce6d16abb35940d7805fe210f1ad614ee0a7fe8596e1905d304fa6eff6daf9b2

    We reuse its verified six-file TESS snapshot and measured stellar pulse frequency. Pulse coefficients remain free in every event. We do not copy its analysis code.

  4. usesLocal fits to six TESS sectors do not resolve a KELT-9 b eclipse depth change from 2019 to 2024 sci:sha256:a6203af39c5839b4acca6c41bd66edb381d894a74311589743fb8b933c7f02a7

    This publication is an intermediate source in the FITS provenance chain credited by the pulse study. We preserve this source credit with the unchanged data.

  5. Two transit models with quadratic baselines give KELT-9 b mean times 42–53 seconds apart in six TESS sectors sci:sha256:e778f30bfcea5d95785e6c8aba96c2a094f17c6f0d8da31e454153a02d391bf9

    Its catalog abstract reports differences between symmetric and asymmetric timing fits. This is context for the free asymmetric profiles used here. It is not a source of our duration measurements.

  6. usesdoi:10.17909/t9-nmc8-f686

    NASA TESS, SPOC, and MAST supply the six public 120-second light curves. Exact filenames, hashes, archive URLs, and processing headers identify the reused source version.

  7. usesdoi:10.3847/1538-4357/ac6b9a

    We integrate equations 4 and 5 with the best parameters in Tables 2 and 3. We then compute a circular-star duration prediction. This earlier work already detected nodal precession with spectra.

  8. usesdoi:10.3847/1538-3881/ab8fa3

    This paper supplies gravity-darkening context and the Table 1 theoretical limb coefficients used as initial synthetic test values. Our tests do not integrate its rotating stellar surface model.

  9. doi:10.3847/1538-3881/aba2cb

    Prior work established the stellar pulse that must be separated from the transit profile.

  10. doi:10.1051/0004-6361/202243823

    This prior gravity-darkening analysis permits changes in the stellar pulse. It gives context for independent pulse coefficients in each event.

  11. usesdoi:10.48550/arXiv.2602.01446

    Earlier SCI work credits this paper through TEPCat for the period and epoch used to locate event windows. Our event centers are free fit parameters.

  12. usesdoi:10.1086/683602

    The batman software supplies independent synthetic transits and a uniform-star overlap check.

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