Pauline Arriaga, University of California, Los Angeles
Michael P. Fitzgerald, University of California, Los Angeles
Gaspard Duchêne, University of California, Berkeley
Paul Kalas, University of California, Berkeley
Maxwell A. Millar-Blanchaer, Jet Propulsion Laboratory
Marshall D. Perrin, Space Telescope Science Institute
Christine H. Chen, Space Telescope Science Institute
Johan Mazoyer, Jet Propulsion Laboratory
Mark Ammons, Lawrence Livermore National Laboratory
Vanessa P. Bailey, Jet Propulsion Laboratory
Trafis S. Barman, The University of Arizona
Joanna Bulger, National Institutes of Natural Sciences - National Astronomical Observatory of Japan
Jeffrey K. Chilcote, University of Notre Dame
Tara Cotten, University of Georgia
Robert J. De Rosa, European Southern Observatory Santiago
Rene Doyon, Institut de Recherche sur les Exoplanètes
Thomas M. Esposito, University of California, Berkeley
Katherine B. Follette, Amherst College
Benjamin L. Gerard, University of Victoria
Stephen Goodsell, Gemini ObservatorySouthern Operations Center
James R. Graham, University of California, Berkeley
Alexandra Z. Greenbaum, University of Michigan, Ann Arbor
Pascale Hibon, European Southern Observatory Santiago
Justin Hom, School of Earth and Space Exploration
Li Wei Hung, US National Park Service
Patrick Ingraham, Large Synoptic Survey Telescope
Quinn M. Konopacky, Center for Astrophysics & Space Sciences
Bruce A. MacIntosh, Stanford University
Jérôme Maire, Center for Astrophysics & Space Sciences
Franck Marchis, SETI Institute
Mark S. Marley, NASA Ames Research Center
Christian Marois, University of Victoria
Kimberly Ward-Duong, Amherst CollegeFollow
et al, Various Institutions

Document Type


Publication Date


Publication Title

Astronomical Journal


HR4796A hosts a well-studied debris disk with a long history due to its high fractional luminosity and favorable inclination, which facilitate both unresolved and resolved observations. We present new J-and K 1-band images of the resolved debris disk HR4796A taken in the polarimetric mode of the Gemini Planet Imager (GPI). The polarized intensity features a strongly forward-scattered brightness distribution and is undetected at the far side of the disk. The total intensity is detected at all scattering angles and also exhibits a strong forward-scattering peak. We use a forward-modeled geometric disk in order to extract geometric parameters, polarized fraction, and total intensity scattering phase functions for these data as well as H-band data previously taken by GPI. We find the polarized phase function becomes increasingly more forward-scattering as wavelength increases. We fit Mie and distribution of hollow spheres (DHS) grain models to the extracted functions. We find that it is possible to generate a satisfactory model for the total intensity using a DHS model, but not with a Mie model. We find that no single grain population of DHS or Mie grains of arbitrary composition can simultaneously reproduce the polarized fraction and total intensity scattering phase functions, indicating the need for more sophisticated grain models.










© 2020. The American Astronomical Society.


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