Abstract

Abstract In 2018, the near-Earth object (155140) 2005 UD (hereafter UD) experienced a close fly by of the Earth. We present results from an observational campaign involving photometric, spectroscopic, and polarimetric observations carried out across a wide range of phase angles (0.°7–88°). We also analyze archival NEOWISE observations. We report an absolute magnitude of H V = 17.51 ± 0.02 mag and an albedo of p V = 0.10 ± 0.02. UD has been dynamically linked to Phaethon due their similar orbital configurations. Assuming similar surface properties, we derived new estimates for the diameters of Phaethon and UD of D = 5.4 ± 0.5 km and D = 1.3 ± 0.1 km, respectively. Thermophysical modeling of NEOWISE data suggests a surface thermal inertia of and regolith grain size in the range of 0.9–10 mm for UD and grain sizes of 3–30 mm for Phaethon. The light curve of UD displays a symmetric shape with a reduced amplitude of Am(0) = 0.29 mag and increasing at a linear rate of 0.017 mag/° between phase angles of 0° and ∼25°. Little variation in light-curve morphology was observed throughout the apparition. Using light-curve inversion techniques, we obtained a sidereal rotation period P = 5.235 ± 0.005 hr. A search for rotational variation in spectroscopic and polarimetric properties yielded negative results within observational uncertainties of ∼10% μm−1 and ∼16%, respectively. In this work, we present new evidence that Phaethon and UD are similar in composition and surface properties, strengthening the arguments for a genetic relationship between these two objects.

Highlights

  • The Apollo-type near-Earth object (NEO; 155140) 2005 UD was discovered by the Catalina Sky Survey in 2005 (Christensen et al 2005, MPEC 2005-U22). Ohtsuka et al (2006) and Jewitt & Hsieh (2006) showed that it displays orbital properties and photometric colors similar to the wellknown NEO (3200) Phaethon, suggesting a genetic relationship between the two

  • Phaethon is considered to be the parent of three other meteor streams, all belonging to the Geminid meteor complex

  • The inversion software searches for the pole solution and shape model that best fits all of the available light curves

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Summary

Introduction

The Apollo-type near-Earth object (NEO; 155140) 2005 UD (hereafter UD) was discovered by the Catalina Sky Survey in 2005 (Christensen et al 2005, MPEC 2005-U22). Ohtsuka et al (2006) and Jewitt & Hsieh (2006) showed that it displays orbital properties and photometric colors similar to the wellknown NEO (3200) Phaethon, suggesting a genetic relationship between the two. (3200) Phaethon is an intriguing NEO both in terms of orbital elements and physical properties. It displays a highly eccentric orbit (e = 0.89) associated with a very low perihelion distance (q = 0.14 au). Phaethon is considered to be the parent of three other meteor streams, all belonging to the Geminid meteor complex. These streams correspond to the intersection of the orbit of the Earth with that of Phaethon’s at different epochs (Babadzhanov & Obrubov 1987; Jakubík & Neslušan 2015).

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