Photometric Variability and Rotation of β Pictoris b from JWST NIRCam Coronagraphic Imaging
Abstract
We report the detection of photometric variability in the directly imaged super-Jupiter β Pictoris b ( β Pic b). Using JWST NIRCam dual-band coronagraphic imaging, we conducted a 16 hr continuous photometric monitoring campaign in the F210M and F410M filters. We developed and validated a time-series photometry framework that combines point-spread function subtraction, principal component analysis for systematic noise removal, and injection-and-recovery tests to confirm signal fidelity. Both light curves show consistent sinusoidal variability at ∼5 σ and ≫5 σ significance in the F210M and F410M bands, respectively. A joint sinusoidal fit yields a rotation period of P rot = 9.00 ± 0.13 hr and variability amplitudes of 0.85% ± 0.07% and 0.89% ± 0.04% in F210M and F410M, respectively. The near-identical amplitudes and periods in both bands confirm a common astrophysical origin in a heterogeneous atmosphere. Combining P rot with the previously measured projected rotational velocity, we constrain the line-of-sight spin axis inclination of β Pic b. The result favors an equator-on viewing geometry, consistent with line-of-sight spin–orbit alignment: the planetary spin axis, orbital plane, debris disk, and stellar equator are all mutually aligned. This stands in sharp contrast to the large obliquities of wide-separation companions that are likely formed via gravitational fragmentation. Together with the system’s young age, this observation provides independent dynamical evidence that β Pic b formed via core accretion. This result constitutes the first detection of rotational modulation in a close-in, high-contrast exoplanet that likely formed via core accretion, demonstrating that time-series coronagraphic imaging with JWST opens a powerful new window onto the rotation, atmospheric dynamics, and spin–orbit architecture of this population.
Related
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BibTeX
@article{zhou2026photometric,
title = {{Photometric Variability and Rotation of β Pictoris b from JWST NIRCam Coronagraphic Imaging}},
author = {Yifan Zhou and Beth Biller and Aarynn Carter and Marshall Perrin and Michael Poon and Genaro Suárez and Ben J. Sutlieff Ben J. Sutlieff and Johanna Vos and Jason Wang and William Balmer and Marta Bryan and Anthony Boccaletti and Julien Girard and Eileen Gonzales and Jens Kammerer and Jarron Leisenring and Paulina. Palma-Bifani and Kevin Wagner and Dániel Apai and Mickäel Bonnefoy and Brendan Bowler and Kyle Franson and Pengyu Liu and Marcio Meléndez and Stanimir Metchev and Simon Petrus and Laurent Pueyo and Isabel Rebollido and Andrew Skemer and Xianyu Tan and Niall Whiteford},
journal = {The Astronomical Journal},
year = {2026},
month = aug,
doi = {10.3847/1538-3881/ae8bab},
url = {https://hal.science/hal-05845904v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Photometric Variability and Rotation of β Pictoris b from JWST NIRCam Coronagraphic Imaging
AU - Yifan Zhou
AU - Beth Biller
AU - Aarynn Carter
AU - Marshall Perrin
AU - Michael Poon
AU - Genaro Suárez
AU - Ben J. Sutlieff Ben J. Sutlieff
AU - Johanna Vos
AU - Jason Wang
AU - William Balmer
AU - Marta Bryan
AU - Anthony Boccaletti
AU - Julien Girard
AU - Eileen Gonzales
AU - Jens Kammerer
AU - Jarron Leisenring
AU - Paulina. Palma-Bifani
AU - Kevin Wagner
AU - Dániel Apai
AU - Mickäel Bonnefoy
AU - Brendan Bowler
AU - Kyle Franson
AU - Pengyu Liu
AU - Marcio Meléndez
AU - Stanimir Metchev
AU - Simon Petrus
AU - Laurent Pueyo
AU - Isabel Rebollido
AU - Andrew Skemer
AU - Xianyu Tan
AU - Niall Whiteford
PY - 2026
DA - 2026/08/13
JO - The Astronomical Journal
DO - 10.3847/1538-3881/ae8bab
UR - https://hal.science/hal-05845904v1
AB - We report the detection of photometric variability in the directly imaged super-Jupiter β Pictoris b ( β Pic b). Using JWST NIRCam dual-band coronagraphic imaging, we conducted a 16 hr continuous photometric monitoring campaign in the F210M and F410M filters. We developed and validated a time-series photometry framework that combines point-spread function subtraction, principal component analysis for systematic noise removal, and injection-and-recovery tests to confirm signal fidelity. Both light curves show consistent sinusoidal variability at ∼5 σ and ≫5 σ significance in the F210M and F410M bands, respectively. A joint sinusoidal fit yields a rotation period of P rot = 9.00 ± 0.13 hr and variability amplitudes of 0.85% ± 0.07% and 0.89% ± 0.04% in F210M and F410M, respectively. The near-identical amplitudes and periods in both bands confirm a common astrophysical origin in a heterogeneous atmosphere. Combining P rot with the previously measured projected rotational velocity, we constrain the line-of-sight spin axis inclination of β Pic b. The result favors an equator-on viewing geometry, consistent with line-of-sight spin–orbit alignment: the planetary spin axis, orbital plane, debris disk, and stellar equator are all mutually aligned. This stands in sharp contrast to the large obliquities of wide-separation companions that are likely formed via gravitational fragmentation. Together with the system’s young age, this observation provides independent dynamical evidence that β Pic b formed via core accretion. This result constitutes the first detection of rotational modulation in a close-in, high-contrast exoplanet that likely formed via core accretion, demonstrating that time-series coronagraphic imaging with JWST opens a powerful new window onto the rotation, atmospheric dynamics, and spin–orbit architecture of this population.
SN - 0004-6256
SN - 1538-3881
ER -