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Subaru Seminars are usually held in Room 104 of the Hilo Base Facility, adjacent to the main lobby. Everyone is welcome to attend. If you would like to give a seminar, please contact Subaru seminar organizers (Thayne Currie, Tae-Soo Pyo, Nagayoshi Ohashi) by email : (please change"_at" to @).

April 7, Friday, 11 am in 104B

" Diagnosing the Composition of Star-Grazing Bodies in HD 172555, a member of the beta Pictoris Moving Group "

Carol Grady

(NASA-Goddard/Eureka Scientific)

The Earth is thought to have formed in a part of the Solar Nebula deficient in organic material, and to have acquired its water and organics through bombardment by minor bodies. When we directly observe this process we obtain insight into the origin and composition of the bombarding parent bodies. If the system is firmly dated, and a series of such systems identified, we can map when such activity begins, how long it lasts, and the implications for the history of our solar system. The mid-A star β Pictoris provided the first such look into a young planetary system, with imaging of its debris belts (Golimowski et al. 2006), detection of circumstellar gas (Dent et al. 2014; Roberge et al. 2006), and detailed modeling of star- grazing planetesimals (Beust & Morbidelli 2000) which have recently been shown to include water ice dissociation products (Wilson et al. 2016). Temporal variability in these objects was used to predict the existence of a giant planet a decade before its direct imaging discovery (Lagrange et al. 2010). A second star in the same moving group, HD 172555, also has star-grazing bodies. The available spectroscopic data, including HST FUV spectra, demonstrate the presence of super-refractory elements, lithophiles such as silicon ions, as well as more volatile gas including carbon ions and O I. most searches for exoplanetary systems have focussed on two-debris belt systems where warm debris is joined by a Kuiper belt analog. The example of HD 172555 suggests that planet searches should be extended to systems lacking cold debris.

Seminars are also held at JAC, CFHT, and IfA.

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