Probing close-in satellites of Trans-Neptunian Objects through thermal and direct size measurements

TL;DR

This study develops a method combining occultation sizes and thermal data to detect close-in satellites around trans-Neptunian objects, successfully identifying new binary candidates.

Contribution

The paper introduces a novel, separation-independent approach to identify satellites using thermal and occultation data, validated on known binaries and applied to discover new systems.

Findings

Confirmed known binaries with thermal-excess modeling.

Identified three new likely binary systems.

Provided size estimates for potential satellites.

Abstract

Context: Trans-Neptunian objects are distant bodies that retain valuable information about the origin and evolution of the Solar System. Many of these objects constitute binary systems. Studying binaries allows us to further characterise this primitive population and is critical for determining mass densities, a key but elusive physical property. Nevertheless, satellite detection can be challenging. Aims: This study aims to constrain the presence of close-in satellites around a selection of ten trans-Neptunian objects, including four known binary systems used for methodology validation. Methods: We developed a methodology independent of primary-secondary separation. We exploit the combination of occultation-derived sizes and thermal emission data from the "TNOs are Cool" Herschel Space Observatory key project. We model the thermal emission from a binary system to explain the thermal excess that cannot be reproduced by a single body of the occultation-derived size. Results: We obtain satisfactory constraints for the validation targets (208996) Achlys, (229762) G!k\'un{"h\`omd\'im\`a, (38628) Huya and (174567) Varda. We find that (84522) 2002 TC302, (119951) 2002 KX14, and (307261) M\'ani are likely binary systems, which was previously unknown. We report size estimates for their putative satellites. For (84922) 2003 VS2, (28978) Ixion, and (470316) 2007 OC10 we find that no sizable satellite is needed to reconcile thermal and occultation data.