Azimuthal brightness modulation reveals hidden rings in CI Tau
Abstract
Context. Protoplanetary disks often host substructures such as rings and gaps, which trace key processes in planet formation and dust evolution. However, narrow rings may remain unresolved due to limited observational resolution, hiding critical information about early planetesimal formation and the amount of dust present. Aims. We applied the azimuthal brightness modulation method, based on the modulation produced by multiple unresolved optically thick rings embedded in an optically thin background, to multiwavelength ALMA observations of CI Tau to identify unresolved rings and constrain their geometry and optical depth. Methods. We analysed CI Tau archival ALMA continuum observations in bands 3, 6, and 7, and extracted azimuthal brightness profiles along narrow annuli and compared them with forward-modelled synthetic observations of inclined discs containing unresolved rings. Results. We detect the azimuthal signature at ∼22 au in all three bands, consistent with unresolved, optically thick rings embedded in a lower optical depth background. Multiwavelength modelling constrains the rings’ geometry and optical depth, consistent with the conditions expected for streaming instability and early planetesimal formation. Conclusions. Our results demonstrate the applicability of this azimuthal signature technique to real discs, reveal fine-scale dust substructures in CI Tau, and illustrate a new method of studying the early stages of planet formation below the nominal resolution limit.
Related
- JWST Reveals the Kuiper Belt-like Compositions of the Uranian Rings and Small Moons
- JWST Reveals the Kuiper Belt–like Compositions of the Uranian Rings and Small Moons
- Complex Demodulation Reveals Blazhko-like Modulation Fingerprints in Delta Scuti Stars
- The connection between surface brightness and satellite systems for central galaxies through IllustrisTNG (Corrigendum)
- CHEX-MATE: X-ray surface brightness discontinuities across a representative cluster sample
BibTeX
@article{scardoni2026azimuthal,
title = {{Azimuthal brightness modulation reveals hidden rings in CI Tau}},
author = {C E Scardoni and G P Rosotti and F. Zagaria and A. Ribas and Marion Villenave and C J Clarke and R A Booth},
journal = {Astronomy \& Astrophysics - A\&A},
year = {2026},
month = jul,
doi = {10.1051/0004-6361/202660692},
url = {https://hal.science/hal-05771973v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Azimuthal brightness modulation reveals hidden rings in CI Tau
AU - C E Scardoni
AU - G P Rosotti
AU - F. Zagaria
AU - A. Ribas
AU - Marion Villenave
AU - C J Clarke
AU - R A Booth
PY - 2026
DA - 2026/07/16
JO - Astronomy & Astrophysics - A&A
DO - 10.1051/0004-6361/202660692
UR - https://hal.science/hal-05771973v1
AB - Context. Protoplanetary disks often host substructures such as rings and gaps, which trace key processes in planet formation and dust evolution. However, narrow rings may remain unresolved due to limited observational resolution, hiding critical information about early planetesimal formation and the amount of dust present. Aims. We applied the azimuthal brightness modulation method, based on the modulation produced by multiple unresolved optically thick rings embedded in an optically thin background, to multiwavelength ALMA observations of CI Tau to identify unresolved rings and constrain their geometry and optical depth. Methods. We analysed CI Tau archival ALMA continuum observations in bands 3, 6, and 7, and extracted azimuthal brightness profiles along narrow annuli and compared them with forward-modelled synthetic observations of inclined discs containing unresolved rings. Results. We detect the azimuthal signature at ∼22 au in all three bands, consistent with unresolved, optically thick rings embedded in a lower optical depth background. Multiwavelength modelling constrains the rings’ geometry and optical depth, consistent with the conditions expected for streaming instability and early planetesimal formation. Conclusions. Our results demonstrate the applicability of this azimuthal signature technique to real discs, reveal fine-scale dust substructures in CI Tau, and illustrate a new method of studying the early stages of planet formation below the nominal resolution limit.
SN - 0004-6361
SN - 1432-0746
ER -