2007ApJ...671L.165H

We present the discovery of an unusual spatially resolved circumstellar structure associated with the ~90 Myr, nearby, G dwarf star HD 61005. Observations from the FEPS Spitzer Legacy Science survey reveal thermal emission in excess of expected stellar photospheric levels. Follow-up 0.1" resolution HST NICMOS coronagraphic images reveal scattered starlight ≤7" (∼240 AU) from the occulted star (1.1 µm flux density =18±3.3 mJy; and 0.77%±0.16% of the starlight). The extremely high near-IR scattering fraction and IR excess luminosity f=L_IR/L_*~2x10^–3 suggests scattering particle sizes of order a≲1.1 µm/2π∼0.2 µm, comparable to the blowout size (a~0.3 µm) due to radiation pressure from the star. Dust-scattered starlight is traced inward to an instrumental limit of ∼10 AU. The structure exhibits a strong asymmetry about its morphological major axis but is mirror-symmetric about its minor axis.