TESS Pulsation Timing Reveals the JWST Calibration Star HD 158485 as a Double-pulsator Binary
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 Porb=382.80+0.80−0.76~d, eccentricity e=0.242+0.045−0.046, projected light-time amplitudes of 195.8+9.2−8.9 and 239.7+6.8−6.8~s, and a dynamical mass ratio of q=MB/MA=0.818+0.046−0.045. 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~d. 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 PB2-constrained two-atmosphere model differs from the corresponding single-star atmosphere prediction by 1.6\% over 1--5~μm and 2.5\% over 5--28~μm. 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.
Versions
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BibTeX
@misc{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},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.14371},
eprint = {2610.14371},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.14371},
}
RIS
TY - UNPB
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 - 2026/10/09
PB - arXiv
DO - 10.48550/arxiv.2610.14371
UR - https://arxiv.org/abs/2610.14371
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=382.80^+0.80_−0.76~d, eccentricity e=0.242^+0.045_−0.046, projected light-time amplitudes of 195.8^+9.2_−8.9 and 239.7^+6.8_−6.8~s, and a dynamical mass ratio of q=M_B/M_A=0.818^+0.046_−0.045. 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~d. 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 PB2-constrained two-atmosphere model differs from the corresponding single-star atmosphere prediction by 1.6\% over 1--5~μm and 2.5\% over 5--28~μm. 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.
ER -