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Peer-reviewedCC BY 4.0The Astrophysical Journal Letters

TESS Pulsation Timing Reveals the JWST Calibration Star HD 158485 as a Double-pulsator Binary

  • Chenglong Lv1,2
  • Ali Esamdin1,3
  • Shuguo Ma1
  • Shahidin Yaqup1,3
  • Haozhi Wang4
  • Ayzada Jmahali1,3
  • Jianwei Yao1,3
  • Kedieryemu Kamili5
5 affiliations
  1. 1Chinese Academy of Sciences
  2. 2Instituto de Astrofísica de Andalucía—CSIC
  3. 3University of Chinese Academy of Sciences
  4. 4Chinese Academy of Sciences South America Center for Astronomy
  5. 5Xinjiang University
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Abstract

HD 158485 is an A-type δ Scuti star in the CALSPEC network and the JWST absolute-flux calibration program. Gaia DR3 assigns it a binary classification probability close to unity but provides no orbital solution. Using TESS observations from Sectors 14–26, 40–41, 47–60, and 73–86, we measure the pulsation phases of six δ Scuti modes. The frequencies form two groups with opposite light-travel-time delays, revealing two pulsating components. A direct light-curve forward model yields an orbital period of P orb = 382.8 0 − 0.76 + 0.80 days, eccentricity e = 0.24 2 − 0.046 + 0.045 , projected light-time amplitudes of 195 . 8 − 8.9 + 9.2 and 239 . 7 − 6.8 + 6.8 s, and a dynamical mass ratio of q = M B / M A = 0.81 8 − 0.045 + 0.046 . A blind prediction based only on the first two long TESS campaigns reproduces the third campaign without updating the orbital parameters, with a Pearson correlation coefficient of r = 0.983. Its held-out rms is 83.8 s, compared with 289.9 s when the period is fixed at 365.25 days. A 5.15 σ Hipparcos–Gaia EDR3 proper-motion anomaly independently indicates unresolved astrometric motion. The unresolved companion can also affect spectrophotometric predictions: a conditional double-pulsator-binary (PB2)-constrained two-atmosphere model differs from the corresponding single-star atmosphere prediction by 1.6% over 1–5 μ m and 2.5% over 5–28 μ m. HD 158485 therefore shows that a calibration-relevant binary can lack a catalogued orbital solution while two independent pulsation clocks reveal and measure its orbit.

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Cite

BibTeXRIS
BibTeX
@article{lv2026tess,
  title = {{TESS Pulsation Timing Reveals the JWST Calibration Star HD 158485 as a Double-pulsator Binary}},
  author = {Chenglong Lv and Ali Esamdin and Shuguo Ma and Shahidin Yaqup and Haozhi Wang and Ayzada Jmahali and Jianwei Yao and Kedieryemu Kamili},
  journal = {The Astrophysical Journal Letters},
  year = {2026},
  month = oct,
  doi = {10.3847/2041-8213/aeb301},
  url = {https://iopscience.iop.org/article/10.3847/2041-8213/aeb301},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - TESS Pulsation Timing Reveals the JWST Calibration Star HD 158485 as a Double-pulsator Binary
AU  - Chenglong Lv
AU  - Ali Esamdin
AU  - Shuguo Ma
AU  - Shahidin Yaqup
AU  - Haozhi Wang
AU  - Ayzada Jmahali
AU  - Jianwei Yao
AU  - Kedieryemu Kamili
PY  - 2026
DA  - 2026/10/27
JO  - The Astrophysical Journal Letters
DO  - 10.3847/2041-8213/aeb301
UR  - https://iopscience.iop.org/article/10.3847/2041-8213/aeb301
AB  - HD 158485 is an A-type δ Scuti star in the CALSPEC network and the JWST absolute-flux calibration program. Gaia DR3 assigns it a binary classification probability close to unity but provides no orbital solution. Using TESS observations from Sectors 14–26, 40–41, 47–60, and 73–86, we measure the pulsation phases of six δ Scuti modes. The frequencies form two groups with opposite light-travel-time delays, revealing two pulsating components. A direct light-curve forward model yields an orbital period of P orb = 382.8 0 − 0.76 + 0.80 days, eccentricity e = 0.24 2 − 0.046 + 0.045 , projected light-time amplitudes of 195 . 8 − 8.9 + 9.2 and 239 . 7 − 6.8 + 6.8 s, and a dynamical mass ratio of q = M B / M A = 0.81 8 − 0.045 + 0.046 . A blind prediction based only on the first two long TESS campaigns reproduces the third campaign without updating the orbital parameters, with a Pearson correlation coefficient of r = 0.983. Its held-out rms is 83.8 s, compared with 289.9 s when the period is fixed at 365.25 days. A 5.15 σ Hipparcos–Gaia EDR3 proper-motion anomaly independently indicates unresolved astrometric motion. The unresolved companion can also affect spectrophotometric predictions: a conditional double-pulsator-binary (PB2)-constrained two-atmosphere model differs from the corresponding single-star atmosphere prediction by 1.6% over 1–5 μ m and 2.5% over 5–28 μ m. HD 158485 therefore shows that a calibration-relevant binary can lack a catalogued orbital solution while two independent pulsation clocks reveal and measure its orbit.
SN  - 2041-8213
SN  - 2041-8205
ER  -