Detection and characterisation of binary asteroid candidates through stellar occultations
Abstract
Context . Binary asteroids provide key access to fundamental parameters of Solar System remnants and planetary formations. However, the current knowledge of binary asteroids remains strongly biased by observational limitations, and main belt binary systems are still poorly characterised since current techniques preferentially detect either widely separated binaries through direct imaging or close and bright systems via photometry and radar for near-Earth asteroids. In this context, the high-precision astrometry of the Gaia mission has revealed a new population of candidate binaries exhibiting dynamical signatures consistent with unresolved companions. Stellar occultations have therefore emerged as one of the most effective methods to confirm the binary nature of a candidate and improve the current census of intermediate-size systems. Aims . This work is part of the GaiaMoons program, and our aim with it was to characterise a sample of 357 potential binary asteroid targets and confirm or refute their binary nature. The properties of these candidates were derived from the high-precision photometric and astrometric observations provided by the Gaia satellite. Methods . We adopted stellar occultation as the observational method to study these targets. Between October 2023 and February 2026, we successfully carried out 165 observations for 101 targets. We subsequently analysed these events in the context of the available literature and previously reported observations. Results . Out of the 165 observations, 76 led at least to one positive observation. Among these, 33 had at least two positives for 24 objects that have undergone unprecedented occultation observation campaigns, with four objects showing indications of binary or contact binary features, namely (1127) Mimi, (35420) 1998 AG 6 , (206) Hersilia, and (36882) 2000 SW 155 . For the vast majority of these objects, the resulting dataset from all reduced observations provides unique physical and astrometric constraints, as they had never been observed through stellar occultations before. In addition, 89 observations with only negatives allowed the near environment of the targets to be probed. Conclusions . GaiaMoons illustrates how stellar occultation campaigns associated with Gaia observations generate a self-improving cycle to find new binary, thereby probing size and shape to constrain future observations. By standardising this approach, we deliver critical data in unexplored parameter spaces, resolving long-standing observational ambiguities.
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BibTeX
@article{lallemand2026detection,
title = {{Detection and characterisation of binary asteroid candidates through stellar occultations}},
author = {R. Lallemand and J. Desmars and B. Sicardy and Z. Liu and Paolo Tanga and L. Liberato and B. Carry and A. Leroy and Y. Kilic and M. Assafin and A. Siakas and L. Abe and D. Mary and F. Casarramona and D. Smith and D. Antuszewicz and J.-L. Dauvergne and G. Langin and P. Henarejos and P.-L. Phan and F. Braga-Ribas and A. Castro and A. Pal and Á. Sódor and A. Cano Ruiz and A. Pratt and A. Noschese and A. Manna and A. Eberle and A. Schweizer and A. Wendelborn and A. Marciniak and B. Ziółkowski and B. Begiçarslan and B. Kattentidt and C. Tezcan and C. Weber and C. Schnabel and C. Domingues and C. Ziolek and C. Sartini and C. Schäfer and C. Mcpartlin and Cs. Kiss and D. Blazewicz and D. Deneuchatel and D. Herald and D. Dunham and D. Sailing and E. Fonseca Morato and E. Fernandez-Garcia and E. Smith and E. Gradovski and E. Donate Lucas and E. García Navarro and E. Kaan Ülgen and F. Garcia and F. Genc and G. Margoti and G. Arraras},
journal = {Astronomy \& Astrophysics - A\&A},
year = {2026},
month = aug,
doi = {10.1051/0004-6361/202660103},
url = {https://hal.science/hal-05764005v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Detection and characterisation of binary asteroid candidates through stellar occultations
AU - R. Lallemand
AU - J. Desmars
AU - B. Sicardy
AU - Z. Liu
AU - Paolo Tanga
AU - L. Liberato
AU - B. Carry
AU - A. Leroy
AU - Y. Kilic
AU - M. Assafin
AU - A. Siakas
AU - L. Abe
AU - D. Mary
AU - F. Casarramona
AU - D. Smith
AU - D. Antuszewicz
AU - J.-L. Dauvergne
AU - G. Langin
AU - P. Henarejos
AU - P.-L. Phan
AU - F. Braga-Ribas
AU - A. Castro
AU - A. Pal
AU - Á. Sódor
AU - A. Cano Ruiz
AU - A. Pratt
AU - A. Noschese
AU - A. Manna
AU - A. Eberle
AU - A. Schweizer
AU - A. Wendelborn
AU - A. Marciniak
AU - B. Ziółkowski
AU - B. Begiçarslan
AU - B. Kattentidt
AU - C. Tezcan
AU - C. Weber
AU - C. Schnabel
AU - C. Domingues
AU - C. Ziolek
AU - C. Sartini
AU - C. Schäfer
AU - C. Mcpartlin
AU - Cs. Kiss
AU - D. Blazewicz
AU - D. Deneuchatel
AU - D. Herald
AU - D. Dunham
AU - D. Sailing
AU - E. Fonseca Morato
AU - E. Fernandez-Garcia
AU - E. Smith
AU - E. Gradovski
AU - E. Donate Lucas
AU - E. García Navarro
AU - E. Kaan Ülgen
AU - F. Garcia
AU - F. Genc
AU - G. Margoti
AU - G. Arraras
PY - 2026
DA - 2026/08/14
JO - Astronomy & Astrophysics - A&A
DO - 10.1051/0004-6361/202660103
UR - https://hal.science/hal-05764005v1
AB - Context . Binary asteroids provide key access to fundamental parameters of Solar System remnants and planetary formations. However, the current knowledge of binary asteroids remains strongly biased by observational limitations, and main belt binary systems are still poorly characterised since current techniques preferentially detect either widely separated binaries through direct imaging or close and bright systems via photometry and radar for near-Earth asteroids. In this context, the high-precision astrometry of the Gaia mission has revealed a new population of candidate binaries exhibiting dynamical signatures consistent with unresolved companions. Stellar occultations have therefore emerged as one of the most effective methods to confirm the binary nature of a candidate and improve the current census of intermediate-size systems. Aims . This work is part of the GaiaMoons program, and our aim with it was to characterise a sample of 357 potential binary asteroid targets and confirm or refute their binary nature. The properties of these candidates were derived from the high-precision photometric and astrometric observations provided by the Gaia satellite. Methods . We adopted stellar occultation as the observational method to study these targets. Between October 2023 and February 2026, we successfully carried out 165 observations for 101 targets. We subsequently analysed these events in the context of the available literature and previously reported observations. Results . Out of the 165 observations, 76 led at least to one positive observation. Among these, 33 had at least two positives for 24 objects that have undergone unprecedented occultation observation campaigns, with four objects showing indications of binary or contact binary features, namely (1127) Mimi, (35420) 1998 AG 6 , (206) Hersilia, and (36882) 2000 SW 155 . For the vast majority of these objects, the resulting dataset from all reduced observations provides unique physical and astrometric constraints, as they had never been observed through stellar occultations before. In addition, 89 observations with only negatives allowed the near environment of the targets to be probed. Conclusions . GaiaMoons illustrates how stellar occultation campaigns associated with Gaia observations generate a self-improving cycle to find new binary, thereby probing size and shape to constrain future observations. By standardising this approach, we deliver critical data in unexplored parameter spaces, resolving long-standing observational ambiguities.
SN - 0004-6361
SN - 1432-0746
ER -