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Broad-band photometry of the Ultra-fast Rotator 2014 GN1.

ATel #6065; M. Hicks (JPL/Caltech), I. Harley (PCC) J. Frederick (PCC),
on 13 Apr 2014; 01:05 UT
Credential Certification: Michael D. Hicks (Michael.Hicks@jpl.nasa.gov)

Subjects: Optical, Asteroid, Planet (minor), Solar System Object, Near-Earth Object

The small near-Earth asteroid 2014 GN1 was discovered by the Mount Lemmon Sky Survey on April 2, 2014 (MPEC 2014-G20). Although the object's orbit passes very close to the Earth's orbit (Minimum Orbit Intersection Distance MOID = 0.0027 AU), it is too small (H > 22 mag) to be considered a Potentially Hazardous Asteroid (PHA). The object passed within 0.0063 AU (2.5 Lunar Distances) on April 6, 2014.

We obtained two partial nights of Bessel R-band photometry near Earth close-approach at the JPL Table Mountain 0.6-m telescope on April 5 and 6 2014, as illustrated in Figure 1, 2 and summarized in Table 1. After correcting for heliocentric and geocentric distance, we were able to construct a solar phase curve and solve for absolute magnitude H_R=23.70+/-0.02 mag and solar phase parameter g=0.04, as shown in Figure 3 . The solar phase curve of 2014 GN1 is steep (slope coefficient b=0.041 mag/deg) and implies a relatively low albedo rho=0.07+/-0.02 (Belskaya & Shevchenko 2000). Assuming a V-R color consistent with a low albedo C-type asteroid (V-R=0.40 mag), we estimate the absolute magnitude in the V-band H_V = 24.1, significantly brighter than the absolute magnitude H_V=24.63 listed in the JPL small-body database. We expect that the effective diameter of 2014 GN1 lies within 70m and 90m.

After converting the time-resolved photometry of April 6, 2014 to flux units we applied standard Fourier techniques. Figure 4 plots the chi squared model misfit as a function of assumed rotational period, with a single clear minimum near 0.27 hr. Figure 5 plots our phased lightcurve assuming our measured period of 16.548+/-0.012 min. 2014 GN is an monolithic fast rotator, with a shape maintained by a non-zero tensile strength.

Copyright 2014. 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 AST-1156756 to Los Angeles City College.

Table 1: Observational summary. 
                                    Rate of   Exp. 
UT Date     r   delta phase   V      motion length    Observers 
           [AU]  [AU] [deg]  [mag] [deg/day] [sec] 
Apr 05.25 1.014 0.015  27.5  16.8     18.9    180     Hicks 
Apr 06.21 1.003 0.007  70.7  16.3     94.5     90     Frederick, Harley, Hicks