The AKARI IRC asteroid flux catalogue: updated diameters and albedos

Abstract

The AKARI IRC All-sky survey provided more than twenty thousand thermal infrared observations of over five thousand asteroids. Diameters and albedos were obtained by fitting an empirically calibrated version of the standard thermal model to these data. After the publication of the flux catalogue in October 2016, our aim here is to present the AKARI IRC all-sky survey data and discuss valuable scientific applications in the field of small body physical properties studies. As an example, we update the catalogue of asteroid diameters and albedos based on AKARI using the near-Earth asteroid thermal model (NEATM). We fit the NEATM to derive asteroid diameters and, whenever possible, infrared beaming parameters. We fit groups of observations taken for the same object at different epochs of the survey separately, so we compute more than one diameter for approximately half of the catalogue. We obtained a total of 8097 diameters and albedos for 5170 asteroids, and we fitted the beaming parameter for almost two thousand of them. When it was not possible to fit the beaming parameter, we used a straight line fit to our sample's beaming parameter-versus-phase angle plot to set the default value for each fit individually instead of using a single average value. Our diameters agree with stellar-occultation-based diameters well within the accuracy expected for the model. They also match the previous AKARI-based catalogue at phase angles lower than 50 degrees, but we find a systematic deviation at higher phase angles, at which near-Earth and Mars-crossing asteroids were observed. The AKARI IRC All-sky survey is an essential source of information about asteroids, especially the large ones, since, it provides observations at different observation geometries, rotational coverages and aspect angles. For example, by comparing in more detail a few asteroids for which dimensions were derived from occultations, we discuss how the multiple observations per object may already provide three-dimensional information about elongated objects even based on an idealised model like the NEATM. Finally, we enumerate additional expected applications for more complex models, especially in combination with other catalogues.

Thermal properties of large main-belt asteroids observed byHerschelPACS

“…For each target, we estimated the Bond albedo (necessary input) as the average value obtained from the different radiometric diameters available from AKARI and/or WISE (Usui et al 2011;Alí-Lagoa et al 2018;Mainzer et al 2016), and all available H-G, H-G 12 , and H-G 1 -G 2 values from the Minor Planet Center, Oszkiewicz et al (2011), or Vereš et al (2015.…”

“…Müller 2002;Müller & Blommaert 2004;Emery et al 2006;Müller et al 2017;Landsman et al 2018) and/or from allsky thermal IR surveys (e.g. Delbo' & Tanga 2009;Alí-Lagoa et al 2014;Rozitis et al 2014;Hanuš et al 2015Hanuš et al , 2016Bach et al 2017;Marciniak et al 2018) had been used to model ∼100 asteroids with TPMs. With the recent addition of another 100 (Hanuš et al 2018b), WISE data are now the single largest source of asteroid thermal inertias.…”

Expected spectral characteristics of (101955) Bennu and (162173) Ryugu, targets of the OSIRIS-REx and Hayabusa2 missions

“…Comparison of the distributions of taxonomic classes found for each family. We have grouped the Polana-Eulalia complex and the Clarissa family (left), and the Erigone and Sulamitis families (right) to enhance the similarities between each pair.We have also computed the average geometric albedo for each family, using WISE/NEOWISE data(Wright et al 2010;Mainzer et al 2011), the NEATM model implemented byAlí-Lagoa et al (2017), and values for H and G 12 from Oszkiewicz et al(2012). These average albedos and their associated errors are shown in…”

“TNOs are Cool”: A survey of the trans-Neptunian region

“…Flux density upper limits were treated in the same way as described in Vilenius et al (2014). While the beaming parameter has a dependence on the phase angle (see, e.g., Delbo et al 2003;Ali-Lagoa et al 2018), this cannot be considered in our cases due to the very limited phase angle ranges.…”