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[75.09] Does the 3.3 micron feature require UV excitation?

T.L. Smith (Space Science Institute, Columbus), G.C. Clayton (Louisiana State University)

The so-called unidentified infrared (UIR) emission features at 3.3, 6.2, 7.7, 8.6 and 11.3 \mum have been studied in many astrophysical objects and their origin has been attributed to polycyclic aromatic hydrocarbons (PAHs). Past observations show that UIRs can be detected in UV-rich environments, however, the coolest object observed to have well-defined UIR features is vdB 133, illuminated by the binary system HD 195593 (A+B), which includes an F5Iab (T_eff \approx 6800 K) and a B7II (T_eff \approx 12000 K)-type star. Recently, a new astronomical PAH model (Li & Draine 2002) successfully reproduced the UIBs found in the "UV-weak environment" of vdB 133.

We wanted to address the question of whether the 3.3 \mum feature requires UV photons for excitation, and if so, to determine the lower-limit. Toward that end, thirteen stars, ranging in temperature from 15000 K to 3500 K, were observed using SpeX at the NASA Infrared Telescope Facility (IRTF) in August and September, 2002.

Li, A., & Draine, B.T. 2002, ApJ, 572, 232.

The author(s) of this abstract have provided an email address for comments about the abstract: tsmith@campbell.mps.ohio-state.edu

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.