SPITZER MID-IR SPECTRA OF DUST DEBRIS AROUND A AND LATE B TYPE STARS: ASTEROID BELT ANALOGS AND POWER-LAW DUST DISTRIBUTIONS

摘要: Using the Spitzer/Infrared Spectrograph (IRS) low-resolution modules covering wavelengths from 5 to 35 μm, we observed 52 main-sequence A and late B type stars previously seen using Spitzer/Multiband Imaging Photometer (MIPS) have excess infrared emission at 24 μm above that expected stellar photosphere. The mid-IR is confirmed in all cases but two. While prominent spectral features are not evident any of spectra, a striking diversity overall shape energy distributions. Most IRS spectra consistent with single-temperature blackbody emission, suggestive dust located single orbital radius—a narrow ring. Assuming originates population large grains, temperatures range 70 324 K, median 190 K corresponding distance 10 AU. Thirteen however, follows power-law distribution, F_ν = F 0λ^α, exponent α ranging 1.0 2.9. warm these systems must span greater locations—an extended disk. All also been Spitzer/MIPS 27 50 sources detected (signal-to-noise ratio > 3). fluxes cooler, Kuiper Belt-like component may be completely independent asteroid belt-like wavelengths. Fourteen 37 blackbody-like fits μm. 13 objects fit by disk model, (four above, three on, six below extrapolated power law), suggesting far-IR related for sources. Overall, thermal profiles reveal debris distributed wide variety radial structures do appear correlated or age. An additional 43 fainter without photometry were Spitzer/IRS; results summarized Appendix B.