Absolute colours and phase coefficients of trans-Neptunian objects: HV − HR and relative phase coefficients

Abstract

The trans-Neptunian objects (TNOs) are small Solar System bodies at large distances from the Sun. As such, their physical properties are difficult to measure. Accurate determination of their physical parameters is essential to model and theorize the actual composition and distribution of the population, and to improve our understanding of the formation and evolution of the Solar System. The objective of this work is to construct phase curves in two filters, V and R, of a large TNO sample obtaining absolute magnitudes (H) and phase coefficients (β), and study possible relations between them and other physical parameters (orbital elements, sizes, and albedos). We used our own data, together with data from the literature, to create the phase curves assuming an overall linear trend. We obtained new magnitudes for 35 TNOs, 27 in the V filter and 35 in the R filter. These magnitudes, together with data from the literature, allowed us to obtain absolutes magnitudes, 114 in the V filter and 113 in the R filter, of which 106 have both. From the search for correlations we found a strong anticorrelation between H V − H R and ∆β = β V − β R , which is probably more related to surface structure than to composition or size of the objects.

Phase Curves of Small Bodies from the SLOAN Moving Objects Catalog

“…In Fig. 17 we show the absolute colors vs. the difference in G. There seem to be weak anticorrelations (see Table 6) between these quantities, possibly analogous to these found for TNOs (Ayala-Loera et al 2018;Alvarez-Candal et al 2019). In the latter work, we proposed it was related to a predominance of single-scattering at a low-phase angle, but the same cannot be said here because, first, G is not the same as the phase coefficient β obtained from a simple linear model, and second, the PCs in this work are mostly of asteroids obtained at a wide range of phase angles (see the right panel of Fig.…”

“…We generated 10 000 different solutions of the PCs for each run by varying each magnitude within their errors following m * = m + rand i , where rand i is a random number extracted from a normal distribution with σ = σ m . This is based on the method developed and tested in Alvarez-Candal et al (2016 and Ayala-Loera et al (2018) for TNOs. Note that it may happen that some of the 10 000 runs resulted in non-valid solutions.…”

Absolute colours and phase coefficients of trans-Neptunian objects: correlations and populations

“…(1) In Ayala-Loera et al (2018) we identified a strong relation between the absolute colour and the relative phase coefficients for a sample of 106 objects, this relationship holds regardless of location in the outer Solar System and size. In this work we confirm that it is present among the different dynamical classes, therefore, it must be a property of the particles forming the surface of the bodies, rather than composition, perhaps due to the size-particle distribution and/or inter-particle spacing.…”

Hubble Space Telescope Search for Activity in High-perihelion Objects

“…Similar diversity was reported by Rabinowitz et al (2007), who also noted that the phase functions of Centaurs tend to be linear with α. Additional phase function measurements, also showing a wide scatter, are given in Alvarez-Candal et al (2016) and Ayala-Loera et al (2018). Motivated by these results, and in the interests of simplicity, we write 2.5 log 10 (Φ(α)) = −βα, where β = 0.061±0.002 magnitudes per degree is the mean value of the V-filter phase coefficients reported for seven Centaurs in Table 4 of Rabinowitz et al (2007).…”