Characterisation of Transneptunian Binaries in the HST Archive.

Binary Transneptunian Objects (TNOs) have remained virtually unaltered since the formation of the solar system. They can therefore provide valuable insights into the history and properties of objects from the outer solar system, such as object compositions and dynamical history, including the effects of planetary migration on primordial planetesimal populations. Benecchi et al. 2009 measured the colours of 23 TNO binaries using the Hubble Space Telescope (HST), reporting a strong correlation between primary-secondary F606W-F814W colours. Marsset et al. 2020 extended this work into the NIR, adding a further three TNO binary objects with accurate colour measurements made using the Gemini-North telescope which indicated a similar colour correlation in the infrared.

   We aim to increase the number of binary TNOs with accurate NIR colour measurements by reprocessing data available in the HST archive using a consistent MCMC-based point spread function (PSF)-fitting algorithm. We explore both the position and brightness parameter space for the binary components. Tiny Tim (Krist et al., 2011) PSFs are generated for each component and planted in a model image that is compared with the HST archive image to identify best-fit PSF parameter values. These values are then used to produce and subtract a final model image, providing accurate likelihood estimates for the in-image position and photometric brightness of each component.

   We will present the results of applying the algorithm to archival data of 24 known binaries, including both optical and NIR colour measurements of both binary components. We will also provide a measure of our sensitivity to binary component separations and brightness ratios. Our results will be compared to the correlated colours observed by Benecchi et al. (2009) and Marsset et al. (2020).

 

References:

S. D. Benecchi, K. S. Noll, W. M. Grundy, M. W. Buie, D. C. Stephens, andH. F. Levison. The correlated colors of transneptunian binaries. Icarus, 200(1):292–303, Mar 2009. doi: 10.1016/j.icarus.2008.10.025.

J Krist, R Hook, and F Stoehr. 20 years of hubble space telescope opticalmodeling using tiny tim, 2011. URLhttps://doi.org/10.1117/12.892762.

Micha ̈el Marsset, Wesley C. Fraser, Michele T. Bannister, Megan E. Schwamb, Rosemary E. Pike, Susan Benecchi, J. J. Kavelaars, Mike Alexandersen, Ying-Tung Chen, Brett J. Gladman, Stephen D. J. Gwyn, Jean-Marc Petit, and Kathryn Volk. Col-OSSOS: Compositional Homogeneity of Three KuiperBelt Binaries.The Planetary Science Journal, 1(1):16, June 2020. doi:10.3847/PSJ/ab8cc0.