Broadband photometry of 2005 YU55: Solar phase behavior and absolute magnitude.
ATel #3763; M. Hicks (JPL/Caltech), J. Somers (Moorpark College), T. Truong (CSULA), S. Teague (VVC), C. Strojia (VVC)
on 14 Nov 2011; 23:06 UT
Credential Certification: Michael D. Hicks (Michael.Hicks@jpl.nasa.gov)
Subjects: Optical, Asteroid, Planet (minor), Solar System Object, Near-Earth Object, Potentially Hazardous Asteroid
The Near-Earth Asteroid (NEA) 2005 YU55 was discovered at Kitt Peak by R.
McMillan on Dec 28 2005 (M.P.E.C. 2005-Y47). With an absolute magnitude H_V =
21.9 mag and an Minimum Orbit Intersection Distance MOID = 0.0011 AU, this
object has been designated as Potentially Hazardous Asteroid (PHA) by the Minor
Planet Center. The asteroid recently made an exceptionally close approach to the
Earth, passing within 0.0217 AU (325,000 KM) on 2011-Nov-08 23:28. An optical
spectrum obtained at the Palomar Hale Telescope in the object's 2010 apparition
(Hicks et al., ATel #2571) was found consistent with C-type taxonomy, suggesting
a very low-albedo and a surface composition similar to the carbonaceous
chondrite meteorites.
Two partial nights of Bessel R photometry at the JPL Table Mountain (TMO) 0.6-m
telescope during the 2010 and 2011 apparitions, as summarized in Table 1. The
time-resolved observed R-band magnitudes are plotted in Figures
1
and
2.
The photometry from both nights is compatible with a relatively slow rotation
rate and a low lightcurve amplitude. The wide range of solar phase angle
observed on 2011-Nov-09 (70 to 43 deg) and the 2011-Apr-17 data (33 to 35 deg)
allowed us to fit a standard HG model (H_R = 20.73 mag, G = -0.12), as shown in
Figure 3. The phase curve of 2005 YU55 is very steep, similar to other low-albedo
C-type and P-type asteroids. Using an effective V-R color measured from our
spectrum, we estimate an absolute magnitude H_V = 21.1+/-0.1 mag, significantly
brighter than earlier estimates. Assuming an albedo of 0.05, we estimate the
diameter D ~ 360+/-20 m. Our lightcurve photometry is too sparse for an
independent lightcurve analysis, we welcome collaborations with other
researchers.
Copyright 2011. All rights reserved. The research described in this telegram was
carried out at the Jet Propulsion Laboratory, under a contract with the National
Aeronautics and Space Administration. The student participation was supported by
the National Science Foundation under REU grant 0852088 to Cal State LA.
Table 1: Observational circumstances.
----nightly averaged----
Solar Num.
UT DATE r delta Phase V Exp. Observers
[AU] [AU] [deg] [mag]
2010 04 17.21 1.023 0.023 34.3 15.2 120 Somers, Hicks
2011 06 15.27 0.992 0.003 54.8 11.1 184 Hicks, Truong, Teague, Strojia
