EF Cha: Warm Dust Orbiting a Nearby 10 Myr Old Star

TL;DR

EF Cha, a young star approximately 10 million years old, exhibits warm dust in its terrestrial planet zone, indicating active planet formation processes and second-generation dust production, unlike the cold dust typically seen in older stars.

Contribution

This study identifies EF Cha as a nearby young star with warm, second-generation dust, providing evidence of ongoing terrestrial planet formation in a star system only 10 million years old.

Findings

EF Cha shows prominent mid-infrared excess due to warm dust.

Spectroscopy reveals small, amorphous, and crystalline silicate grains.

Warm dust survival time is less than 100,000 years, indicating recent dust production.

Abstract

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 Sun's 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.