TAXONOMIC CLASSIFICATIONS OF ASTEROIDS<\/p>\n
David J. Tholen
\n Institute for Astronomy
\n 2680 Woodlawn Drive
\n Honolulu, HI 96822<\/p>\n
Since the last Asteroids book was published, there have been two taxonomic
\nclassification schemes developed and applied to the body of available color
\nand albedo data (Tholen, 1984; Barucci et al., 1987). Asteroid taxonomic
\nclassifications according to these schemes are reproduced in the table. The
\nBarucci et al. classifications have been copied directly from the paper they
\npublished in Icarus. Their classifications are based on a combination of
\neight-color photometry and IRAS albedos. The Tholen classifications are
\nessentially the same as those supplied to the IRAS Asteroid Advisory Group
\nin November, 1983, and as such, are not based on the IRAS albedos. This list
\nconsists of the classifications tabulated in Tholen (1984), but extended by a
\nrigorous application of the classification scheme to those objects with UBV
\ncolors (Bowell et al., 1979), and a non-rigorous application to those objects
\nwith 24-color spectra (Chapman and Gaffey, 1979). A few of the classifications
\ngiven here disagree with the ones given by Tholen (1984). These discrepancies
\nare flagged in the Notes column. In some cases, the classifications of objects
\nin the X and C spectral classes are based on unpublished albedos provided by
\nTedesco and Gradie. Although IRAS albedos are available that would permit the
\nelimination of some classification ambiguities, caution is advised when
\napplying IRAS albedos, because in many cases the IRAS fluxes have been
\noverestimated, resulting in underestimated albedos.<\/p>\n
Two differences between Tholen’s 1984 list and this list are apparent. The
\nletter X has been used to stand for E or M or P. Tholen (1984) used EMP,
\nwhich could be misinterpreted as meaning E is most likely, M is next most
\nlikely, and P is least likely. Note that the E, M, and P classes are
\nspectrally degenerate, so in the absence of albedo information, their similar
\nspectra can be represented by a single letter. Also, the letter I has been
\nintroduced to stand for Inconsistent data. In Tholen (1984), 515 Athalia was
\ngiven a stand-alone U classification, due to its S-type spectrum but uniquely
\nlow albedo. However, because of the desire to use U as only a suffix, the
\nletter I was introduced.<\/p>\n
The following notation appears in the classifications:
\n U suffix indicating an unusual spectrum; falls far from cluster center
\n : suffix indicating noisy data
\n :: suffix indicating very noisy data
\n — indicates data that are too noisy to permit classification
\n (essentially all types would be allowed)<\/p>\n
Due to popular demand, orbital group designations have been included in this
\ntable. The 2- or 3-letter abbreviations stand for the following groups:
\n ATE Aten
\n APO Apollo
\n AMO Amor
\n MC Mars crosser
\n HUN Hungaria
\n PHO Phocaea
\n GRI Griqua
\n CYB Cybele
\n HIL Hilda
\n TRO Trojan<\/p>\n
Explanatory notes and references are given in file TAXONOMY.NOT. This list
\nwas revised as of 1988 March 20 and therefore supercedes earlier tabulations.<\/p>\n
