Multi-Epoch Stability in the Rotational Modulation of the Planetary-Mass Companion Ross 458C
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 HST/WFC3 observations more than 7.5 yr before and published by Manjavacas et al. (2019). 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 micron), obtaining a value of 1.47+\-0.18%, which is consistent with that measured in the HST/WFC3 light curve.
Related
- Discovery and Characterization of the TOI-4468 Planetary System: A Transiting Hot Jupiter with a Lone Nearby Outer Companion
- A Search for Persistent Rotational Modulation in the Dedicated TESS Observations of Interstellar Comet 3I/ATLAS
- Orbital Stability of Apsidally Aligned Planetary Systems
- Space Journey Beyond Earth: Exploring the properties of exoplanets and multi-planetary systems
- Companion architectures of sub-Saturns: Distinct migration pathways across the Neptunian landscape
BibTeX
@misc{manjavacas2026multiepoch,
title = {{Multi-Epoch Stability in the Rotational Modulation of the Planetary-Mass Companion Ross 458C}},
author = {Elena Manjavacas and Jared Bull and Paulo Miles-Paez and Natalia Oliveros-Gomez and Theodora Karalidi and Ben W. P. Lew and Zhoujian Zhang and Yifan Zhou and Daniel Apai and Xianyu Tan},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22072},
eprint = {2609.22072},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22072},
}
RIS
TY - UNPB
TI - Multi-Epoch Stability in the Rotational Modulation of the Planetary-Mass Companion Ross 458C
AU - Elena Manjavacas
AU - Jared Bull
AU - Paulo Miles-Paez
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 - 2026/09/18
PB - arXiv
DO - 10.48550/arxiv.2609.22072
UR - https://arxiv.org/abs/2609.22072
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 HST/WFC3 observations more than 7.5 yr before and published by Manjavacas et al. (2019). 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 micron), obtaining a value of 1.47+\-0.18%, which is consistent with that measured in the HST/WFC3 light curve.
ER -