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تسجيل مستخدم جديدThe Ch-class asteroids: Connecting a visible taxonomic class to a 3-{mu}m band shape
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Asteroids belonging to the Ch spectral taxonomic class are defined by the presence of an absorption near 0.7 {mu}m, which is interpreted as due to Fe-bearing phyllosilicates. Phyllosilicates also cause strong absorptions in the 3-{mu}m region, as do other hydrated and hydroxylated minerals and H2O ice. Over the past decade, spectral observations have revealed different 3-{mu}m band shapes the asteroid population. Although a formal taxonomy is yet to be fully established, the Pallas-type spectral group is most consistent with the presence of phyllosilicates. If Ch class and Pallas type are both indicative of phyllosilicates, then all Ch-class asteroids should also be Pallas-type. In order to test this hypothesis, we obtained 42 observations of 36 Ch-class asteroids in the 2- to 4-{mu}m spectral region. We found that 88% of the spectra have 3-{mu}m band shapes most consistent with the Pallas-type group. This is the first asteroid class for which such a strong correlation has been found. Because the Ch class is defined by the presence of an absorption near 0.7 {mu}m, this demonstrates that the 0.7-{mu}m band serves not only as a proxy for the presence of a band in the 3-{mu}m region, but specifically for the presence of Pallas-type bands. There is some evidence for a correlation between band depth at 2.95 {mu}m and absolute magnitude and/or albedo. However, we find only weak correlations between 2.95-{mu}m band depth and semi-major axis. The connection between band depths in the 0.7- and 3-{mu}m regions is complex and in need of further investigation.
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