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تسجيل مستخدم جديدEF Cha: Warm Dust Orbiting a Nearby 10 Myr Old Star
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Most Vega-like stars have far-infrared excess (60micron or longward in IRAS, ISO, or Spitzer MIPS bands) and contain cold dust (<~150K) analogous to the Suns Kuiper-Belt region. However, dust in a region more akin to our asteroid belt and thus relevant to the terrestrial planet building process is warm and produces excess emission in mid-infrared wavelengths. By cross-correlating Hipparcos dwarfs with the MSX catalog, we found that EF Cha, a member of the recently identified, ~10 Myr old, ``Cha-Near Moving Group, possesses prominent mid-infrared excess. N-band spectroscopy reveals a strong emission feature characterized by a mixture of small, warm, amorphous and possibly crystalline silicate grains. Survival time of warm dust grains around this A9 star is <~ 1E5 yrs, much less than the age of the star. Thus, grains in this extra-solar terrestrial planetary zone must be of second generation and not a remnant of primodial dust and are suggestive of substantial planet formation activity. Such second generation warm excess occurs around ~ 13% of the early-type stars in nearby young stellar associations.
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