A precise TESS ephemeris for the short-period binary TIC-259864042

Abstract

This paper presents a precise eclipse-timing analysis of TIC 259864042 (= EC 02406--6408, Gaia DR3 4647004122914240640) using eleven sectors of TESS photometry spanning 2018--2025 (7.1 yr). The system exhibits a single deep eclipse with a V-shaped profile at phase 0 and no detectable counterpart at phase 0.5. Four independent period-search methods converge to a common period agreeing to within 7 parts per million. An independent reduction with the SHERLOCK pipeline, using its own 120-second TESS photometry, confirms the same period at the same precision. A joint linear ephemeris fit gives P = 0.46048676 ± 0.0000001 d (11.059 h) and T_0 = 2458325.70381 ± 0.00002 BJD, with a residual RMS of 0.87 min across the 7.1-yr baseline. Per-sector ephemeris fits show residual medians within ±0.42 min of zero, confirming that no cycle slip has occurred across the large TESS data gaps. The period is stable at the level of ΔBIC = +5.21 (in favour of the constant-period model); an upper limit of |Ṗ| ≤ 1 × 10⁻⁹ d d⁻¹ is placed on any secular period change. A PHOEBE 2.4 fit to the Sector 27 light curve yields i = 80.8^∘ ± 0.5^∘, R₁ = 0.21 ± 0.01 R_⊙, R₂ = 0.25 ± 0.02 R_⊙, q = 0.49 ± 0.07, consistent with a grazing detached geometry and a mid-M-dwarf companion. The TESS light curve alone cannot distinguish between the two temperatures 25100 K and 31000 K. The paper discusses the system in the context of the sdB eclipsing binary population, and notes that while the current data are consistent with a short-period sdB+M-dwarf architecture, a phase-resolved spectrum is needed to independently confirm the sdB identification.

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BibTeX

@misc{khan2026precise,
  title = {{A precise TESS ephemeris for the short-period binary TIC-259864042}},
  author = {Rana Khan},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.31076},
  eprint = {2610.31076},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.31076},
  note = {CC0},
}

RIS

TY  - UNPB
TI  - A precise TESS ephemeris for the short-period binary TIC-259864042
AU  - Rana Khan
PY  - 2026
DA  - 2026/10/22
PB  - arXiv
DO  - 10.48550/arxiv.2610.31076
UR  - https://arxiv.org/abs/2610.31076
AB  - This paper presents a precise eclipse-timing analysis of TIC 259864042 (= EC 02406--6408, Gaia DR3 4647004122914240640) using eleven sectors of TESS photometry spanning 2018--2025 (7.1 yr). The system exhibits a single deep eclipse with a V-shaped profile at phase 0 and no detectable counterpart at phase 0.5. Four independent period-search methods converge to a common period agreeing to within 7 parts per million. An independent reduction with the SHERLOCK pipeline, using its own 120-second TESS photometry, confirms the same period at the same precision. A joint linear ephemeris fit gives P = 0.46048676 ± 0.0000001 d (11.059 h) and T_0 = 2458325.70381 ± 0.00002 BJD, with a residual RMS of 0.87 min across the 7.1-yr baseline. Per-sector ephemeris fits show residual medians within ±0.42 min of zero, confirming that no cycle slip has occurred across the large TESS data gaps. The period is stable at the level of ΔBIC = +5.21 (in favour of the constant-period model); an upper limit of |Ṗ| ≤ 1 × 10^−9 d d^−1 is placed on any secular period change. A PHOEBE 2.4 fit to the Sector 27 light curve yields i = 80.8^∘ ± 0.5^∘, R_1 = 0.21 ± 0.01 R_⊙, R_2 = 0.25 ± 0.02 R_⊙, q = 0.49 ± 0.07, consistent with a grazing detached geometry and a mid-M-dwarf companion. The TESS light curve alone cannot distinguish between the two temperatures 25100 K and 31000 K. The paper discusses the system in the context of the sdB eclipsing binary population, and notes that while the current data are consistent with a short-period sdB+M-dwarf architecture, a phase-resolved spectrum is needed to independently confirm the sdB identification.
ER  -

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