Asteroid systems such as binaries and pairs are indicative of physical
properties and dynamical histories of the Small Solar System Bodies. Although
numerous observational and theoretical studies have been carried out, the
formation mechanism of asteroid pairs is still unclear, especially for
near-Earth asteroid (NEA) pairs. We conducted a series of optical photometric
and polarimetric observations of a small NEA 2010 XC15β in 2022 December to
investigate its surface properties. The rotation period of 2010 XC15β is
possibly a few to several dozen hours and color indices of 2010 XC15β are
derived as gβr=0.435Β±0.008, rβi=0.158Β±0.017, and rβz=0.186Β±0.009 in
the Pan-STARRS system. The linear polarization degrees of 2010 XC15β are a
few percent at the phase angle range of 58β to 114β. We found
that 2010 XC15β is a rare E-type NEA on the basis of its photometric and
polarimetric properties. Taking the similarity of not only physical properties
but also dynamical integrals and the rarity of E-type NEAs into account, we
suppose that 2010 XC15β and 1998 WT24β are of common origin (i.e.,
asteroid pair). These two NEAs are the sixth NEA pair and first E-type NEA pair
ever confirmed, possibly formed by rotational fission. We conjecture that the
parent body of 2010 XC15β and 1998 WT24β was transported from the
main-belt through the Ξ½6β resonance or Hungaria region.Comment: Resubmitted to AAS Journals. Any comments are welcom