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astro-ph.SR · Solar and Stellar Astrophysics

Four TESS SAP light curves show that the eclipse interval of KW Hydrae increased from 2019 to 2026

This study measures the time from a primary eclipse to the next secondary eclipse of KW Hydrae in four public TESS visits. The data are the 120-second SPOC light curves from sectors 8, 35, 61, and 99. Fits to 18 complete eclipses in the simple aperture photometry (SAP) flux give an increase of 9.24 +/- 0.23 seconds per year over 6.94 years. The last visit interval exceeds the first by 64.44 +/- 1.68 seconds. The errors include a circular block estimate of correlated residual noise. They assume independent events and do not include all model or calibration errors. Removing one visit gives rates from 9.05 to 9.56 seconds per year. The corrected PDCSAP flux gives 26.86 +/- 2.62 seconds per year with scaled white noise errors and much larger residuals. Thus the precise rate depends on the flux product and has no confirmation from a separate aperture extraction. The SAP result is consistent with the known apsidal motion of this binary under published orbit assumptions. This study extends the timing record to 2026. It does not claim the first apsidal motion detection or evidence for a planet. The package preserves the four source FITS files, archive search and hashes, event fits, controls, noise checks, figures, source code, and reproduction instructions.

KW Hydrae · TESS · eclipsing binaries · eclipse timing · apsidal motion · correlated noise · SAP · PDCSAP · public data

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References

9
  1. usesdoi:10.1051/0004-6361/202040004

    This paper gives the first apsidal motion result for KW Hya, the reference ephemeris and stellar parameters, and the prior theoretical rate. Our trend fit shares sector 8 but uses no historical eclipse interval.

  2. usesdoi:10.1051/0004-6361/201935837

    The eccentricity of the adopted orbit is from this interferometric and velocity study, as used by Baroch et al. (2021).

  3. doi:10.3847/1538-4357/ac75c2

    This later study uses the prior Baroch et al. rate for KW Hya. It is part of the search for earlier results.

  4. doi:10.1093/mnras/stae165

    This TESS variability survey lists TIC 60658382. It provides search context. No numerical result from it enters our fit.

  5. usesdoi:10.1086/683602

    The batman quadratic limb darkening calculation supplies the spherical eclipse flux model.

  6. usesdoi:10.17909/ha89-1n96

    We use the public sector 8 TESS SPOC 120-second light curve for TIC 60658382.

  7. usesdoi:10.17909/817a-tx86

    We use the public sector 35 TESS SPOC 120-second light curve for TIC 60658382.

  8. usesdoi:10.17909/9t2q-b830

    We use the public sector 61 TESS SPOC 120-second light curve for TIC 60658382.

  9. usesdoi:10.17909/bptp-t156

    We use the public sector 99 TESS SPOC 120-second light curve for TIC 60658382.

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