Palomar Spectroscopy of 2001 FM129, 2004 FG11, and 2005 YU55.

ATel #2571; M. Hicks (JPL/Caltech), K. Lawrence (JPL/Caltech), L. Benner (JPL/Caltech)
on 16 Apr 2010; 23:41 UT
Credential Certification: Michael D. Hicks (Michael.Hicks@jpl.nasa.gov)

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We obtained long-slit CCD spectrograms of the near-Earth asteroids 8254 (2001 FM129), 2004 FG11, and 2005 YU55 using the Palomar 5-m Hale Telescope equipped with the facility dual-channel spectrometer (“Double-Spec”) on April 07 2010. 88254 (2001 FM129) and 2004 FG11 have been designated as Potentially Hazardous Asteroids by the Minor Planets Center. 2005 YU55 in noteworthy as a “virtual impactor”, with a cumulative Earth-impact probability of 7.4e-6 between 2071 and 2109 (http://neo.jpl.nasa.gov/risk/).

Although the night of April 07 was clear, the seeing was poor and variable (FWHM~2-5 arcsec). Table 1 summarizes our observational circumstances, with the expected V magnitude computed assuming a phase parameter G=0.15. Table 2 lists the solar analog stars used to generate the composite normalized reflectance spectra, as shown in Figures 1-3 [1][2][3].

A comparison of our optical spectra with the 1341 asteroid spectra archived in the SMASS II database (Bus & Binzel 2002) was used to determine taxonomy. Table 3 list the five best-fit SMASS II analogs for each object. Our asteroids cover a wide range of surface composition: 2004 FG11 (V-type), 2001 FM129 (Sq-type), and 2005 YU55 (C-type). Additional data, specifically optical lightcurves, near-IR spectra, and thermal flux measurements obtained over the remainder of their current apparitions would be very useful to further constrain the nature of these objects.

Copyright 2010 California Institute of Technology. Government sponsorship acknowledged.

  
Table 1: Observational Circumstances.  
  
Object Name   r (AU)  delta (AU)  p (deg)  H (mag)  V (mag)  Exp Time (min)  
2001 FM129    1.229     0.341      41.9     17.5     17.3       55.0  
2004 FG11     1.034     0.079      62.9     20.9     17.7       50.0  
2005 YU55     1.095     0.095       6.4     21.8     17.4       55.0  

  
Table 2:  Solar Analog Stars  
  
Object Name      Solar Analog Stars  
2001 FM129       RU149B  
2004 FG11        16 Cyg B  
2005 YU55        RU149B, 102-370, 105-56, 107-98, 110-361  

  
Table 3:  Best-fit SMASS II spectral analogs.  
  
                          TAXONOMIC CLASS  
MISFIT  OBJECT NAME        (THOLEN) (BUS)  
  
    - for 2001 FM129 -  
0.923  4733 ORO                       Sq  
0.933   180 Garumna           S       Sq  
0.936  2873 Binzel                    Sq  
0.971  3903 Kliment Ohridski          Sq  
0.986  4968 Suzamur                   Sq  
  
    - for 2004 FG11 -  
2.220  4311 Zguridi                   V  
2.411  3498 Belton                    V  
2.437  2547 Hubei                     V  
2.465  3536 Schleicher                V  
2.514  3265 Fletcher                  V  
  
    - for 2005 YU55 -  
1.034  2378 Pannekoek                 Cgh  
1.056   826 Henrika                   C  
1.063   392 Wilhelmina                Ch  
1.071   106 Dione             G       Cgh  
1.082  3827 Zdenekhorsky              C