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Mid-infrared spectra of dust debris around main-sequence stars

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  • Physics


MID-INFRARED SPECTRA OF DUST DEBRIS AROUND MAIN-SEQUENCE STARS1 M. Jura,2 C. H. Chen,3 E. Furlan,4 J. Green,5 B. Sargent,5 W. J. Forrest,5 D. M. Watson,5 D. J. Barry,4 P. Hall,4 T. L. Herter,4 J. R. Houck,4 G. C. Sloan,4 K. Uchida,4 P. D’Alessio,6 B. R. Brandl,7 L. D. Keller,8 F. Kemper,2,9 P. Morris,10 J. Najita,11 N. Calvet,12 L. Hartmann,12 and P. C. Myers12 Receivved 2004 March 26; accepted 2004 May 27 ABSTRACT We report spectra obtained with the Spitzer Space Telescope in the k ¼ 14 35 �m range of 19 nearby main- sequence stars with infrared excesses. The six stars with strong dust emission show no recognizable spectral features, suggesting that the bulk of the emitting particles have diameters larger than 10 �m. If the observed dust results from collisional grinding of larger solids, we infer minimum masses of the parent body population between 0.004 and 0.06 M�. We estimate grain production rates of �1010 g s�1 around k Boo and HR 1570; selective accretion of this matter may help explain their peculiar surface abundances. There appear to be inner truncations in the dust clouds at 48, 11, 52, and 54 AU around HR 333, HR 506, HR 1082, and HR 3927, respectively. Subject headinggs: circumstellar matter — infrared: stars 1. INTRODUCTION The discovery with IRAS of a large infrared excess around Vega (Aumann et al. 1984) initiated the detailed study of other planetary systems. We can now use the dust emission from main-sequence stars to constrain models for the origin and evolution of these environments (Lagrange et al. 2000; Zuckerman 2001) with the long-term goal of developing a more comprehensive understanding of the formation and evolution of planets and related minor bodies. Most previous studies of the dust around main-sequence stars have been re- stricted to using broadband infrared fluxes (e.g., Habing et al. 2001; Spangler et al. 2001). Here we report measurements with the Infrared Spectrograph ( IRS; Houck et al. 2004)13 on the Spitzer Space Telescope (Werner et al.

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