Asteroids' satellites in Gaia astrometric data
Authors: Liberato Luana , Tanga Paolo , Mary David 
Published: July 2024

It is known to the astronomical community that asteroids with satellites are not uncommon in the Solar System. So far we have more than 500 documented asteroid systems encompassing binaries, pairs and multiples[1]. Yet, amidst this group of objects, several others remain enigmatic due to the challenges in observation and detection with conventional observation techniques such as adaptive optics, radar or photometric methods.&#160;Thanks to the ultra-high precision provided by Gaia DR3, we were able to develop a method to search for satellites around asteroids using astrometric measurements for more than 150,000 asteroids. Our approach is based on the effects in the orbits of the asteroids due to the gravitational perturbation of a companion. Since the astrometric data provides information on the photocenter of the object, the post-orbital fit residuals may present signatures of a wobble of the photocenter around the system's barycenter, as detected for the asteroid (4337) Arecibo[2]. &#160;After the detection of a periodic wobble in the data we adopt a simple model for interpreting wobbling signals, characterized by spherical components with uniform albedo. Kepler's 3rd law allows us to identify the systems with parameters such as densities and separations within a physically meaningful range of values. We perform a series of statistical tests and physical properties filters in order to obtain the most significant and consistent list of astrometric binary candidates.&#160;This approach yields a preliminary selection of 358 potential candidates. With additional knowledge of taxonomic types, we can refine our density constraints, resulting in a narrowed list of 67 asteroid binary candidates. While some of these candidates coincide with the distribution of small photometric binaries, others occupy parameter spaces often overlooked by conventional techniques.&#160;In this work, we present our first search for astrometric asteroid binaries in Gaia DR3[3], along with the preliminary analysis of the method using Gaia FPR data and additional applications of Gaia astrometry in the estimation of some binary system's physical properties.References[1] Johnston, Wm. Robert. "Asteroids with Satellites Database" May 10, 2024. Johnston's Archive.[2] Gaia Collaboration Tanga, P., et al. 2023, Astronomy and Astrophysics 674 A12, https://doi.org/10.1051/0004-6361/202243796[3] Liberato, L. et al. 2024, Astronomy and Astrophysics, Accepted for publicationAcknowledgementsThis work presents results based on data from the Gaia mission (ESA) processed by the Gaia Data Processing and Analysis Consortium (DPAC). DPAC is funded by national institutions, in particular those participating in the Gaia MultiLateral Agreement (MLA) (Gaia mission website and archive: https://www.cosmos.esa.int/gaia and \\https://archives.esac.esa.int/gaia). The project was supported by the Coordena&#231;&#227;o de Aperfei&#231;oamento de Pessoal de N&#237;vel Superior &#8211; Brasil (CAPES) &#8211; Finance Code 001, and CAPES-PRINT Process 88887.570251/2020-00, by the French Agence Nationale de la Recherche, ANR, &#8220;GaiaMoons&#8221; ANR-22-CE49-0002-01, the Programme National de Planetologie, and the BQR program of Observatoire de la C&#244;te d&#8217;Azur.&#160;