Spitzer mid-ir spectra of dust debris around a and late b type stars

Asteroid belt analogs and power-law dust distributions

Farisa Y. Morales, M. W. Werner, G. Bryden, P. Plavchan, K. R. Stapelfeldt, George H. Rieke, K. Y L Su, C. A. Beichman, C. H. Chen, K. Grogan, S. J. Kenyon, A. Moro-Martin, S. Wolf

Research output: Contribution to journalArticle

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Abstract

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) to have excess infrared emission at 24 μm 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 ν = F 0λα, with exponent α 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 μm, with 27 of the 50 excess sources detected (signal-to-noise ratio > 3). Most 70 μm 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 μm. The 13 objects with IRS excess emission fit by a power-law disk model, however, are all detected at 70 μm (four above, three on, and six below the extrapolated power law), suggesting that the mid-IR IRS emission and far-IR 70 μm 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 μm photometry were also observed with Spitzer/IRS; results are summarized in Appendix B.

Original languageEnglish (US)
Pages (from-to)1067-1086
Number of pages20
JournalAstrophysical Journal
Volume699
Issue number2
DOIs
StatePublished - 2009

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asteroid belts
debris
asteroid
power law
dust
analogs
spectrographs
stars
wavelength
Kuiper belt
orbitals
power law distribution
distribution
photometer
photosphere
spectral energy distribution
coolers
wavelengths
signal-to-noise ratio
photometry

Keywords

  • Circumstellar matter
  • Infrared: stars
  • Planetary systems: formation

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Spitzer mid-ir spectra of dust debris around a and late b type stars : Asteroid belt analogs and power-law dust distributions. / Morales, Farisa Y.; Werner, M. W.; Bryden, G.; Plavchan, P.; Stapelfeldt, K. R.; Rieke, George H.; Su, K. Y L; Beichman, C. A.; Chen, C. H.; Grogan, K.; Kenyon, S. J.; Moro-Martin, A.; Wolf, S.

In: Astrophysical Journal, Vol. 699, No. 2, 2009, p. 1067-1086.

Research output: Contribution to journalArticle

Morales, FY, Werner, MW, Bryden, G, Plavchan, P, Stapelfeldt, KR, Rieke, GH, Su, KYL, Beichman, CA, Chen, CH, Grogan, K, Kenyon, SJ, Moro-Martin, A & Wolf, S 2009, 'Spitzer mid-ir spectra of dust debris around a and late b type stars: Asteroid belt analogs and power-law dust distributions', Astrophysical Journal, vol. 699, no. 2, pp. 1067-1086. https://doi.org/10.1088/0004-637X/699/2/1067
Morales, Farisa Y. ; Werner, M. W. ; Bryden, G. ; Plavchan, P. ; Stapelfeldt, K. R. ; Rieke, George H. ; Su, K. Y L ; Beichman, C. A. ; Chen, C. H. ; Grogan, K. ; Kenyon, S. J. ; Moro-Martin, A. ; Wolf, S. / Spitzer mid-ir spectra of dust debris around a and late b type stars : Asteroid belt analogs and power-law dust distributions. In: Astrophysical Journal. 2009 ; Vol. 699, No. 2. pp. 1067-1086.
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AU - Bryden, G.

AU - Plavchan, P.

AU - Stapelfeldt, K. R.

AU - Rieke, George H.

AU - Su, K. Y L

AU - Beichman, C. A.

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AU - Grogan, K.

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AU - Moro-Martin, A.

AU - Wolf, S.

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