SPITZER MID-IR SPECTRA OF DUST DEBRIS AROUND A AND LATE B TYPE STARS: ASTEROID BELT ANALOGS AND POWER-LAW DUST DISTRIBUTIONS
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
- NASA Exoplanet Science Institute (NExScI), California Institute of Technology, 770 S. Wilson Ave, Pasadena, CA 91125 (United States)
- Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
- Space Telescope Science Institute (STScI), 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08540 (United States)
Using the Spitzer/Infrared Spectrograph (IRS) low-resolution modules covering wavelengths from 5 to 35 {mu}m, we observed 52 main-sequence A and late B type stars previously seen using Spitzer/Multiband Imaging Photometer (MIPS) to have excess infrared emission at 24 {mu}m above that expected from the stellar photosphere. The mid-IR excess is confirmed in all cases but two. While prominent spectral features are not evident in any of the spectra, we observed a striking diversity in the overall shape of the spectral energy distributions. Most of the IRS excess spectra are consistent with single-temperature blackbody emission, suggestive of dust located at a single orbital radius-a narrow ring. Assuming the excess emission originates from a population of large blackbody grains, dust temperatures range from 70 to 324 K, with a median of 190 K corresponding to a distance of 10 AU. Thirteen stars however, have dust emission that follows a power-law distribution, F {sub {nu}} = F {sub 0}{lambda}{sup {alpha}}, with exponent {alpha} ranging from 1.0 to 2.9. The warm dust in these systems must span a greater range of orbital locations-an extended disk. All of the stars have also been observed with Spitzer/MIPS at 70 {mu}m, with 27 of the 50 excess sources detected (signal-to-noise ratio > 3). Most 70 {mu}m fluxes are suggestive of a cooler, Kuiper Belt-like component that may be completely independent of the asteroid belt-like warm emission detected at the IRS wavelengths. Fourteen of 37 sources with blackbody-like fits are detected at 70 {mu}m. The 13 objects with IRS excess emission fit by a power-law disk model, however, are all detected at 70 {mu}m (four above, three on, and six below the extrapolated power law), suggesting that the mid-IR IRS emission and far-IR 70 {mu}m emission may be related for these sources. Overall, the observed blackbody and power-law thermal profiles reveal debris distributed in a wide variety of radial structures that do not appear to be correlated with spectral type or stellar age. An additional 43 fainter A and late B type stars without 70 {mu}m photometry were also observed with Spitzer/IRS; results are summarized in Appendix B.
- OSTI ID:
- 21333761
- Journal Information:
- Astrophysical Journal, Vol. 699, Issue 2; Other Information: DOI: 10.1088/0004-637X/699/2/1067; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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