On the Bayesian analysis of stellar occultation by small solar system bodies

A stellar occultation occurs when an object (an asteroid, trans-Neptunian object, Centaur) passes in front of a distant star, blocking its light momentarily. The occultation technique allows deriving accurate positions, sizes, and shapes of small solar system objects. The accuracy of the predicted path of the occultation shadow has improved significantly in the last decade, increasing the number of viable targets for study via stellar occultations. The improvement is due mainly to the availability of an accurate astrometric catalog provided by the Gaia mission. In practice, the primary source of uncertainty in the predictions is the uncertainty in the occulting object ephemerides.

The analysis of stellar occultation measurements can be challenging in cases where there is photometry with a low signal-to-noise ratio, a short duration of the event, low temporal or spatial sampling, or a combination of those. Also, we need to account for cases with multiple occulting objects, and multiple occulted stars or combined detection of the same objects at different epochs. In these cases, we can have model parameters with significantly correlated uncertainties and where it is not trivial to discriminate between different models, requiring a rigorous quantitative approach. Last but not less, we need to account for the influence of the model a priori assumptions on the derived parameter values and uncertainties.

Bayesian statistics allow for analysis of these challenging cases, providing posterior probabilities for the object(s) size, shape, and orientation parameters and quantitative comparison of different possible models.

I have adopted a Bayesian approach for analyzing occultations measurements, including multi-epoch detections, single and multi-station detections, single and double objects, and occulting single and double stars.

I will present the application of the approach to the analysis of stellar occultation by Trans-Neptunian objects and Centaurs, exemplified by interesting cases from different projects and collaborations, both published or in the process of publication, including the ringed Centaur (10199) Chariklo, the extreme TNO (541132) Leleākūhonua, the small Centaurs 2014 YY49 and (591376) 2013 NL24, the binary TNO (523764) 2014 WC510, and the retrograde Centaur (342842) 2008 YB3 [1, 2, 3, 4].

 

References:

1. Strauss, Leiva, Buie et al. 2021. PSJ, 2, 1, 22.

2. Leiva, Buie, Keller et al. 2020. PSJ, 1, 2.

3. Buie, Leiva, Keller et al. 2020. AJ 159, 5.

4. Leiva, Sicardy, Camargo et al. 2017. AJ 154, 4.