The Moth: An Unusual Circumstellar Structure Associated with HD 61005
Henning, Thomas; Schneider, Glenn; Hines, Dean C.; Bouwman, Jeroen; Meyer, Michael R.; Moro-Martín, Amaya; Hillenbrand, Lynne A.; Mamajek, Eric E.; Carpenter, John M.; Kim, Jinyoung Serena; Hollenbach, David; Wolf, Sebastian; Metchev, Stanimir A.; Silverstone, Murray D.
United States, Germany
Abstract
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=LIR/L*~2×10-3 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.