THE FORMATION AND EVOLUTION OF PLANETARY SYSTEMS (FEPS): DISCOVERY OF AN UNUSUAL DEBRIS SYSTEM ASSOCIATED WITH HD 12039

We report the discovery of a debris system associated with the 30 Myr old G3/5V star HD 12039 using Spitzer Space Telescope observations from 3.6–160 m. An observed infrared excess (LIR /L 1; 104) above the ex-pected photosphere for k k14 m is fit by thermally emittingmaterial with a color temperature of T 110K, warmer than the majority of debris disks identified to date around Sun-like stars. The object is not detected at 70 mwith a 3 upper limit 6 times the expected photospheric flux. The spectrum of the infrared excess can be explained bywarm, op-tically thinmaterial comprised of blackbody-like grains of sizek7m that reside in a belt orbiting the star at 4–6AU. An alternate model dominated by smaller grains, near the blowout size a 0:5 m, located at 30–40 AU is also pos-sible but requires the dust to have been produced recently, since such small grains will be expelled from the system by radiation pressure in approximately a few times 102 yr. Subject headinggs: circumstellar matter — infrared: stars — planetary systems: protoplanetary disks — stars: individual (HD 12039) 1