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Peer-reviewedCC BY 4.0The Astrophysical Journal Letters

Multiepoch Stability in the Rotational Modulation of the Planetary-mass Companion Ross 458C

  • Elena Manjavacas1,2
  • Jared Bull2
  • Paulo Miles-Paéz3
  • Natalia Oliveros- Gomez2
  • Theodora Karalidi4
  • Ben W. P. Lew5,6
  • Zhoujian Zhang7
  • Yifan Zhou8
  • Daniel Apai9
  • Xianyu Tan10
10 affiliations
  1. 1Space Telescope Science Institute
  2. 2Johns Hopkins University
  3. 3Centro de Astrobiología
  4. 4University of Central Florida
  5. 5Bay Area Environmental Research Institute
  6. 6NASA Ames Research Center
  7. 7University of Rochester
  8. 8University of Virginia
  9. 9The University of Arizona
  10. 10Tsung-Dao Lee institute and School of Physics and Astronomy
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Abstract

Spectroscopic variability is detected in brown dwarfs across all spectral types, suggesting atmospheric patchiness in brown dwarf atmospheres. We present JWST/NIRSpec time series observations of the T8.0 planetary-mass companion Ross 458C. We compared our derived spectral variability and light curve to those obtained using Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) observations more than 7.5 yr before and published by E. Manjavacas et al. We found that the light curve of Ross 458C is remarkably similar in the two epochs in terms of shape and variability amplitude potentially created by stable weather patterns. We measured a rotational period of 11.57 ± 0.09 hr, demonstrating that the previously reported HST/WFC3 period of 6.75 ± 1.58 hr is most likely a second-order harmonic produced by an unresolved double-peaked rotational modulation, likely due to the higher uncertainties of the HST/WFC3 light curve and the short time baseline of those observations. We measured the variability amplitude in the white light curve created using only the wavelength range covered by HST/WFC3 (1.10–1.63 μ m), obtaining a value of 1.47% ± 0.18%, which is consistent with that measured in the HST/WFC3 light curve.

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Cite

BibTeXRIS
BibTeX
@article{manjavacas2026multiepoch,
  title = {{Multiepoch Stability in the Rotational Modulation of the Planetary-mass Companion Ross 458C}},
  author = {Elena Manjavacas and Jared Bull and Paulo Miles-Paéz and Natalia Oliveros- Gomez and Theodora Karalidi and Ben W. P. Lew and Zhoujian Zhang and Yifan Zhou and Daniel Apai and Xianyu Tan},
  journal = {The Astrophysical Journal Letters},
  year = {2026},
  month = nov,
  doi = {10.3847/2041-8213/aeaae4},
  url = {https://iopscience.iop.org/article/10.3847/2041-8213/aeaae4},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Multiepoch Stability in the Rotational Modulation of the Planetary-mass Companion Ross 458C
AU  - Elena Manjavacas
AU  - Jared Bull
AU  - Paulo Miles-Paéz
AU  - Natalia Oliveros- Gomez
AU  - Theodora Karalidi
AU  - Ben W. P. Lew
AU  - Zhoujian Zhang
AU  - Yifan Zhou
AU  - Daniel Apai
AU  - Xianyu Tan
PY  - 2026
DA  - 2026/11/02
JO  - The Astrophysical Journal Letters
DO  - 10.3847/2041-8213/aeaae4
UR  - https://iopscience.iop.org/article/10.3847/2041-8213/aeaae4
AB  - Spectroscopic variability is detected in brown dwarfs across all spectral types, suggesting atmospheric patchiness in brown dwarf atmospheres. We present JWST/NIRSpec time series observations of the T8.0 planetary-mass companion Ross 458C. We compared our derived spectral variability and light curve to those obtained using Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) observations more than 7.5 yr before and published by E. Manjavacas et al. We found that the light curve of Ross 458C is remarkably similar in the two epochs in terms of shape and variability amplitude potentially created by stable weather patterns. We measured a rotational period of 11.57 ± 0.09 hr, demonstrating that the previously reported HST/WFC3 period of 6.75 ± 1.58 hr is most likely a second-order harmonic produced by an unresolved double-peaked rotational modulation, likely due to the higher uncertainties of the HST/WFC3 light curve and the short time baseline of those observations. We measured the variability amplitude in the white light curve created using only the wavelength range covered by HST/WFC3 (1.10–1.63 μ m), obtaining a value of 1.47% ± 0.18%, which is consistent with that measured in the HST/WFC3 light curve.
SN  - 2041-8213
SN  - 2041-8205
ER  -