Silica-Rich Bright Debris Disk around HD 15407A
  We report an intriguing debris disk towards the F3V star HD 15407A, in which an extremely large amount of warm fine dust (~ 10^(-7) M_Earth) is detected. The dust temperature is derived as ~ 500-600 K and the location of the debris dust is estimated as 0.6-1.0 AU from the central star, a terrestrial planet region. The fractional luminosity of the debris disk is ~ 0.005, which is much larger than those predicted by steady-state models of the debris disk produced by planetesimal collisions. The mid-infrared spectrum obtained by Spitzer indicates the presence of abundant micron-sized silica dust, suggesting that the dust comes from the surface layer of differentiated large rocky bodies and might be trapped around the star. 
Hideaki Fujiwara, Takashi Onaka, Takuya Yamashita, Daisuke Ishihara,   Hirokazu Kataza, Misato Fukagawa, Yoichi Takeda, and ...
astro-ph.EP