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Published December 20, 2007 | Published
Journal Article Open

The moth : an unusual circumstellar structure associated with HD 61005


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_* ≈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.

Additional Information

© 2007 The American Astronomical Society. Received 2007 June 29; accepted 2007 October 31; published 2007 November 21. We have benefited from discussions with P. Kalas and M. Wyatt. GO 10527 HST observations are supported by NASA through a grant from the Space Telescope Science Institute. FEPS acknowledges support from NASA contracts 1224768 and 1224566 administered through the Jet Propulsion Laboratory.

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