The recent dynamical past of the low perihelion NEO population

The NEO population model derived by Granvik et al. (2016,2017,2018) suggested that there is an overestimate of objects in low perihelion distance (q) orbits when compared to the observed population. The remedy to this discrepancy was to include a super-catastrophic disruption of objects when they crossed an average disruption distance, defined as q*=0.076 au. The mechanism responsible for destroying such objects is not determined yet, but it is believed to be thermal in nature.

In this study, we aim to determine which members of the known NEO population have approached close to the Sun in their recent past and may exhibit signs of disintegration. These can be the targets of more detailed studies ranging from Earth-based observations to space missions for in-situ measurements.

 

We have selected all NEOs that have q<0.5 au and have been observed for at least 28 days. This resulted in a set of 842 both numbered and unnumbered objects. Next, we extracted the astrometry data for all objects from the MPC database. We used OpenOrb to compute the orbits of all the selected NEOs and generated 49 additional clones. We modified swift_rmvs3 to be able to perform integrations backward in time. The orbits of all objects were then  integrated for -0.5 Myr, including all the planets, Pluto and the Moon in the simulations. For each object, we determined how far back in time we can trust the evolution of q, before the effects of chaos kick in. We then determined the minimum q (q_min) that every object has acquired during that time span. 

 

Most of the asteroids observed close to the Sun are typically bright, since dark asteroids are more likely to be destroyed farther from the Sun as a result of thermal effects. For a number of objects, we have information about the corresponding albedos from NEOWISE and SpitzerNEOs, as well as the taxonomic types from Binzel et al. (2009), Devogèle et al. (2019) and Perna et al. (2018)

 

We select the best candidates for showing signs of the effect of extreme solar irradiation and present them in a list that includes their absolute magnitude (H), the reliable time span of the backward integration, the q_min during that time, the standard deviation of q_min, and albedo, spectral slope and spectral type, where available.