2008AJ....136..881K

The Apollo asteroid 1999 YC may share a dynamical association with the Phaethon-Geminid Stream Complex (PGC) (Ohtsuka et al. 2008). Here, we present photometric observations taken to determine the physical properties of 1999 YC. The object shows a nearly neutral reflection spectrum, similar to but slightly redder than the related objects 3200 Phaethon and 2005 UD. Assuming an albedo equal to that of 3200 Phaethon, we find that the diameter is 1.4 ±0.1 km. Time-resolved broadband photometry yields a double-peaked rotational period of 4.4950±0.0010 h, while the range of the light curve indicates an elongated shape having a projected axis ratio of ∼1.9. Surface brightness models provide no evidence of lasting mass loss of the kind seen in active short-period cometary nuclei. An upper limit to the mass loss is set at ∼10^–3 kg/s, corresponding to an upper limit on the fraction of the surface that could be sublimating water ice of <10^–3. If sustained over the 1000 yr age of the Geminid stream, the total mass loss from 1999 YC (3x10⁷ kg) would be small compared to the reported stream mass (∼10¹²-10¹³ kg), suggesting that the stream is the product of catastrophic, rather than steady-state, breakup of the parent object.