Mid-IR Spectra of Dust Debris around A and late B type Stars: Asteroid Belt Analogs and Power-Law Dust Distributions
First Author:
Farisa Morales
Email: Farisa AT jpl.nasa.gov
JPL
4800 Oak Grove Drive
Pasadena, CA 91109
Coauthors:
Werner, Michael, JPL
Bryden, Geoffrey, JPL
Planchan, Peter, NExScI/IPAC
Stapelfeldt, Karl, JPL
Beichman, Charles, NExScI/IPAC
Chen, Christine, STScI
Grogan, Keith, JPL
Kenyon, Scott, Harvard-Smithsonian
Moro-Martin, Amaya, Princeton
Rieke, George, University of Arizona
Su, Kate, University of Arizona
Wolf, Sebastian, Institut für Theor. Physik und Astrophysik
Abstract
Abstract:
Using the Spitzer/IRS Low-Res modules covering 5 to 35 μm, we observed 52 main-sequence A and late B type stars previously seen from Spitzer/MIPS photometry to have excess emission at 24 μm. While prominent spectral features are not evident, we observed a striking diversity in the overall shape of the spectral energy distributions (SED). Most IRS excess spectra are consistent with blackbody emission, suggestive of dust located at a single orbital radius. The typical T_dust of ∼200 K corresponds to an orbital radius of ∼10 AU. Thirteen stars however, have dust emission that follows a power-law flux distribution, F_ν = F_0 λ^α, with 1.0 ≤ α ≤ 2.9. The warm dust in these systems must span over a greater range of orbital locations. The large number of warm systems tells us that there is still activity in the terrestrial planet zones of both types. All of the stars have also been observed with Spitzer/MIPS at 70 μm, with 27 of the 50 sources detected (S/N > 3). Most 70 μm fluxes are suggestive of a cooler, Kuiper belt-like component that may be independent of the asteroid belt-like warm emission detected at the IRS wavelengths. 14 of 37 sources with blackbody-like fits at IRS wavelengths are detected at 70 μm. The 13 objects with IRS excess emission fit by a power-law model, however, are all detected at 70 μm.
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